Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
Physics 100Prep for Engineering StudiesWinter 2010 – 2011
Dr. Joseph J. TroutDisque [email protected]@drexel.edu
Dimensions:Length Meter (m) Mass Kilogram (kg)Time Second (s)
Dimensions:Length: meter1790 - One ten-millionth of the distance from the equator to either pole.1889 - Platinum- iridium rod1960 - 1,650,763.73 wavelength of orange light produced by krypton-861983 - Distance light travels in 1/ 299,792,458 of a second.
Time: second1/86,400 of a mean solar day9,192,631,770 oscillations of a cesium atom.
Mass: kilogramplatinum – iridium cylinder
Scientific Notation:
1000=103=1 X 103
2000=2 X 1000=2X 103
2345=2.345 X 1000=2.345 X 103
Scientific Notation:
245600000
Scientific Notation:
2456000008 7 6 5 4 3 2 1
Scientific Notation:
245600000=2.456 X 108
8 7 6 5 4 3 2 1
Scientific Notation:
0.015=1.5 X 0.01=1.5 X 1100
=1.5 X 10−2
Prefixes:
yotta Y 1024
zetta Z 1021
exa E 1018
peta P 1015
tera T 1012
giga G 109
mega M 106
kilo k 103
hecto h 102
deka da 101
deci d 10-1
centi c 10-2
milli m 10-3
micro µ 10-6
nano n 10-9
pico p 10-12
femto f 10-15
atto a 10-18
zepto z 10-21
yocto y 10-24
Prefixes:
yotta Y 1024
zetta Z 1021
exa E 1018
peta P 1015
tera T 1012
giga G 109
mega M 106
kilo k 103
hecto h 102
deka da 101
deci d 10-1
centi c 10-2
milli m 10-3
micro µ 10-6
nano n 10-9
pico p 10-12
femto f 10-15
atto a 10-18
zepto z 10-21
yocto y 10-24
Prefixes:
yotta Y 1024
zetta Z 1021
exa E 1018
peta P 1015
tera T 1012
giga G 109
mega M 106
kilo k 103
hecto h 102
deka da 101
deci d 10-1
centi c 10-2
milli m 10-3
micro µ 10-6
nano n 10-9
pico p 10-12
femto f 10-15
atto a 10-18
zepto z 10-21
yocto y 10-24
Prefixes:
Mass
Length
Time
1kilogram=1kg=1000 g=1 X 103g
1centimeter=1cm=0.01m=1 X 10−2m1kilometer=1 km=1000m=1 X 103m
1microsecond=1 s=0.000001 s=1 X 10−6 s1nanosecond=1ns=0.000000001 s=1 X 10−9 s
1mile=1.609 km=1609m1 km=0.621mi1hr=3600 s1 year=3.156 X 107 s1 kg=0.0685 slug1 lb=4.448N
1mile=1.609 km
1mile1.609 km
=1
1.609 km1mile
=1
Conversion Factors:
1mile=1.609 km
1mile1.609 km
=1
5 km=?miles
5 km1mile1.609 km =3.11mi
1mile=1.609 km
5 km=?miles
5 km1mile1.609 km =3.11mi
1hr=3600 s1mi=1609m
20ms=?mph
20ms 1mile1609m
1hr=3600 s1mi=1609m
20ms=?mph
20ms 1mile1609m
1hr=3600 s1mi=1609m
20ms=?mph
20ms 1mile1609m 3600 s
1hr
1hr=3600 s1mi=1609m
20ms=?mph
20ms 1mile1609m 3600 s
1hr =44.75mph
1hr=3600 s1mi=1609m
20ms=?mph
20ms 1mile1609m 3600 s
1hr =44.75mph
1hr=3600 s1mi=1609m
20ms=?mph
20ms 1mile1609m 3600 s
1hr =44.75mph
1hr=3600 s1mi=1609m
60mph=?m /s
60mihr 1609m
1mi 1hr3600 s =26.82m /s
1hr=3600 s1mi=1609m
60mph=?m /s
60mihr 1609m
1mi 1hr3600 s =26.82m /s
1mi=1609m
3mi3=?m3
3mi31609m1mi
3
=1.25 X 1010m3
2mih2 = ________________m
s2
2mih2 1609m
1mi 1h3600 s 2
=2.48 X 10−4m / s2
Scalar – Magnitude only.
Example: mass, distance, speed Example: m, x, v
Vector – Magnitude and Direction.
Example: displacement,velocity, acceleration, forceExample: x ,v ,a , F
Distance – scalar – magnitude of the total distance traveled.
Displacement – vector – distance between final position and initial position AND the direction.
Measurement:
Systematic Error or Uncertainty
Each error in measurement have the same sign.
Example: A meter stick which has been worn down on one side by a millimeter. If you measure something the errors will all add up and the measurement you make will be LONGER than the actual distance.
Measurement:
Random Error or Uncertainty
Chance variations in measurement. These errors are unavoidable. They are just as likely to be positive as negative.These errors can be minimized by taking many measurements and averaging them together.
Example: Three people make a measurement that with the same meter stick but end up with slightly different readings.
Measurement:
Absolute Error
The difference between the value of your measurement and the accepted, published, or theoretical value.
absolute error = experimental value − accepted value
Measurement:Relative Error
The difference between the value of your measurement and the accepted, published, or theoretical value “compared” to the accepted, published, or theoretical value.
relative error = experimental value − accepted value accepted value
% rel err = exp value − acc value acc value
X 100 %
Measurement:Relative Error
Accepted Value g=9.80m/ s2
Measured Value g=9.76m / s2
Absolute Error =9.76m/ s2−9.80m / s2=−0.04m / s2
Measurement:Relative Error
Accepted Value g=9.80m/ s2
Measured Value g=9.76m/ s2
Absolute Error =9.76m / s2−9.80m/ s2=−0.04m/ s2
Rel Error =9.76m/ s2−9.80m / s2
9.8m / s2 =−0.0041
Measurement:Relative Error
Accepted Value g=9.80m/ s2
Measured Value g=9.76m/ s2
Absolute Error =9.76m / s2−9.80m/ s2=−0.04m/ s2
Rel Error =9.76m/ s2−9.80m / s2
9.8m / s2 =−0.0041
% Rel Error =9.76m/ s2−9.80m/ s2
9.8m/ s2 X 100%=−0.41 %
PRECISIONThe degree of consistency or reproducibility of a measurement.The more precise the measurement, the less the difference between two observations of the same event.
PRECISIONMost skilled observer can not estimate readings better than 1/10 of the smallest division.
Example: If the smallest division on a meter stick is a cm, then the best you could hopefully estimate would be 1/10 of a cm or 1 mm.
1.0 2.0 3.0 4.0 5.0 cm
1.0 2.0 3.0 4.0 5.0 cm
L=3.0 cm
1.0 2.0 3.0 4.0 5.0 cm
L=3.5cm
2.0 4.0
L=2.8 cm
1.0 2.0 3.0 4.0
2.0 3.0 4.0
L=2.8 cm
1.0 2.0 3.0 4.0
For most of the experiments in Fundamentals of Physics, you will assume that the best you can estimate a scale reading is 1/10 of the smallest division.
2.0 3.0 4.0
L=2.8cm±0.1cm
1.0 2.0 3.0 4.0
For most of the experiments in Fundamentals of Physics, you will assume that the best you can estimate a scale reading is 1/10 of the smallest division.
Review:
Review
Review 1mile=1609m1km=0.621mi1hr=3600 s1 year=3.156 X 107 s1kg=0.0685 slug1 lb=4.448N
43mph=____________m/ s
Review 1mile=1609m1km=0.621mi1hr=3600 s1 year=3.156 X 107 s1kg=0.0685 slug1 lb=4.448N
43mph=____________m/ s
43mih 1609m
1mi 1h3600 s =19.22m / s
Review 1mile=1609m1km=0.621mi1hr=3600 s1 year=3.156 X 107 s1kg=0.0685 slug1 lb=4.448N
60m/ s=____________mph
60ms 1mi1609m 3600 s
1h =134.24mph
Review 1mile=1609m1km=0.621mi1hr=3600 s1 year=3.156 X 107 s1kg=0.0685 slug1 lb=4.448N
6.0m/ s2=____________mih2
6.0ms2 =1mi1609m 3600 s
1h 2
=4.83 X 104mih2
Review 1mile=1609m1km=0.621mi1hr=3600 s1 year=3.156 X 107 s1kg=0.0685 slug1 lb=4.448N2.54 cm=1 in.
12 in.3=____________ cm3
12 in.32.54 cm1 in.
3
=196.64 cm3=1.9664 X 10−4m
Review 1mile=1609m1km=0.621mi1hr=3600 s1 year=3.156 X 107 s1kg=0.0685 slug1 lb=4.448N2.54 cm=1 in.
12 in.3=____________ cm3
12 in.32.54cm1 in.
3
=196.64 cm3=1.9664 X 10−4m≠1.9664m3
Review 1mile=1609m1km=0.621mi1hr=3600 s1 year=3.156 X 107 s1kg=0.0685 slug1 lb=4.448N2.54 cm=1 in.
12 in.3=____________ cm3
12 in.32.54cm1 in.
3
=196.64 cm3=1.9664 X 10−4m≠1.9664m3
Probably 20 % of the class will make this error in physics one. Don't let it be you.
Measurement:Relative Error
Accepted Value v=3.20m/ sMeasured Value vexp=3.22m/ s
Absolute Error =3.22m/ s−3.20m/ s=0.02m/ s
Rel Error =3.22m / s−3.20m/ s3.20m/ s
=0.00625m/ s
% Rel Error =3.22m/ s−3.20m / s3.20m/ s
X 100%=0.625 %
Review
Reading Significant Figures:
●The first significant figures in a measurement is the first digit other than zero , counting from the left to the right. ●Zeroes to left of the first of the first nonzero digit are not significant.●Zeroes which occur between two significant digits are significant since they are part of the measurement.●Final zeros in a measurements containing decimal fractions are significant.●The number of significant digits are independent of the measurement unit.
Reading Significant Figures:
The first significant figures in a measurement is the first digit other than zero , counting from the left to the right.
29.85ml34.002mi53.0 gal
33339.78 km56.34 s
0.003467 ns
Reading Significant Figures:
The first significant figures in a measurement is the first digit other than zero , counting from the left to the right.
29.85ml34.002mi53.0 gal
33339.78 km56.34 s
0.003467 ns
Reading Significant Figures:
(2) Zeroes to left of the first of the first nonzero digit are not significant.
0.004ml34.002mi0.2324 gal
0.00004578 km0.34 s
Reading Significant Figures:
(2) Zeroes to left of the first of the first nonzero digit are not significant.
0.004ml34.002mi0.2324 gal
0.00004578 km0.34 s
Reading Significant Figures:
(3)Zeroes which occur between two significant digits are significant since they are part of the measurement.
0.004ml34.002mi0.2324 gal
0.00004578 km0.3004 s
Reading Significant Figures:
(3)Zeroes which occur between two significant digits are significant since they are part of the measurement.
0.004ml34.002mi0.2324 gal
0.00004578 km0.3004 s
Reading Significant Figures:
(4) Final zeros in a measurements containing decimal fractions are significant.
0.00400ml34.0020mi0.23240 gal
0.00004578 km0.30040 s
Reading Significant Figures:
(4) Final zeros in a measurements containing decimal fractions are significant.
0.00400ml34.0020mi0.23240 gal
0.00004578 km0.30040 s
Reading Significant Figures:
(5) The number of significant digits are independent of the measurement unit.
10.6 cm=106mm=0.106m=0.000106 km
All have 3 sig figs.
Rounding off Significant FiguresRounding off Significant Figures
42.5444.78
67459.5623.455080.003452
434 4757543
If the first digit to the right of the last significant digit is less than 5, it is dropped.
If the first digit to the right of the last significant digit is greater than or equal to 5, add 1.
Rounding off Significant FiguresRounding off Significant FiguresIf the first digit to the right of the last significant digit is less than 5, it is dropped.
If the first digit to the right of the last significant digit is greater than or equal to 5, add 1.
42.54 42.544.7844.8
67459.566746023.4550823.455
0.0034520.00345
434 4757543
Addition and Subtraction with Addition and Subtraction with Significant FiguresSignificant Figures
Round off to the precision of the least precise measurement.
331.46m / s14.9m / s=331.5m / s14.9m / s=346.4m / s
Addition and Subtraction with Addition and Subtraction with Significant FiguresSignificant Figures
Round off to the precision of the least precise measurement.
60.0mm14.99mm=60.015.0mm=75.0mm
68
Addition and Subtraction with Significant FiguresAddition and Subtraction with Significant Figures
v=2.390 X 102m / s4.5609 X 102m / sv=2.390 X 102m / s4.561 X 102m / s
v=6.951 X 102m / s
T=56.2oF45.234oFT=56.2o F45.2o F
T=111.4oF
69
Multiplication and Division with Significant FiguresMultiplication and Division with Significant Figures
Number of significant figures in the result is no greater than number of significant figures in the measurement with fewest significant figures.
L=34.78cmW=2.767 cm
A=L X W=34.78 cm X 2.767 cm≠96.23626cm=96.24cm
70
Multiplication and Division with Significant FiguresMultiplication and Division with Significant Figures
Number of significant figures in the result is no greater than number of significant figures in the measurement with fewest significant figures.
M = 20.23 kg
l=3.0 cmw=1.0cm
h=2.0cm
71
Multiplication and Division with Significant FiguresMultiplication and Division with Significant Figures
Number of significant figures in the result is no greater than number of significant figures in the measurement with fewest significant figures.
M = 20.23 kg
l=3.6cmw=1.0cm
h=2.8cm
V=l wh=3.6 cm 1.0 cm 2.8 cm=10.08cm3=10.0cm3
72
Multiplication and Division with Significant FiguresMultiplication and Division with Significant Figures
Number of significant figures in the result is no greater than number of significant figures in the measurement with fewest significant figures.
M = 20.23 kg
l=3.6cmw=1.0cm
h=2.8cm
V=l wh=10.08cm3=10 cm3 1.0m100.0 cm
3
=1.0 X 10−5m3
=MV = 20.23kg
1.0 X 10−5m3=2.0 X 106 kg /m3
73
Multiplication and Division with Significant FiguresMultiplication and Division with Significant Figures
Number of significant figures in the result is no greater than number of significant figures in the measurement with fewest significant figures.
l=21.3±0.2cmw=9.80±0.1cm
A=l w=21.3±0.2cm 9.80±0.1cm A≈[21.3cm 9.80 cm ±21.3cm 0.1 cm ±0.2cm 9.80 ±0.2 0.1 ]
A≈209±4 cm2
74
Multiplication and Division with Significant FiguresMultiplication and Division with Significant Figures
Number of significant figures in the result is no greater than number of significant figures in the measurement with fewest significant figures.
l=12.71mw=7.46m
A=l w=12.71 7.46 A=94.8166m2=94.8m2
75
Scientific NotationScientific Notationa=2.0 X 103
b=3.0 X 103
ab=2.0 X 1033.0 X 103=2.03.0 X 103=5.0 X 103
a=1.73 X 105
b=2.9 X 104
ab=1.73 X 1052.9 X 104
ab=1.73 X 1050.29 X 105
ab=2.02 X 105=2.0 X 105
76
Scientific NotationScientific Notationa=1.245 X 103
b=2.70 X 102
a∗b=1.245 X 1032.70 X 102 a∗b=1.245 3.7 103102
a∗b=3.3615 X 105=3.36 X 105
a=6.0 X 108
b=2.0 X 104
a /b=6.0 X 108
2.0 X 104
a /b=6.02.0
X 108−4=3.0 X 104
77
Chapter 11 Plane Geometry
78
A
B
C
Vertex
BAC
79
A
B
CVertex
BAC=90o Right Angle
80
A
BC
Vertex
BAC=180o Straight Angle
81
A
B
CVertex
BAC90o Acute Angle
82
A
B
CVertex
BAC90o Obtuse Angle
83
1
2
1 is acute.2 is obtuse.
1 and 2 are adjacent.
84
12
12=180o
Supplemental Angles Supplemental Angles
85
1
2
12=90o
Complimentary Angles Complimentary Angles
86
1
Vertical Angles Vertical Angles
2
1 ,2
87
1
Vertical Angles Vertical Angles
2
12
1 ,21 ,2
88
12
3
5
4
6
78
3 and 6 ,4 and 5 Alternate Interior. 1 and 8 ,2 and 7 Alternate Exterior.
4 and 6 ,3 and 5 Interior. 1 and 7 ,2 and 8 Exterior.
1 and 5 ,2 and 6,3 and 7,4 and 8 Corresponding.
89
12
3
5
4
6
78
3 and 6 ,4 and 5 Alternate Interior. 1 and 8 ,2 and 7 Alternate Exterior.
4 and 6 ,3 and 5 Interior. 1 and 7 ,2 and 8 Exterior.
1 and 5 ,2 and 6,3 and 7,4 and 8 Corresponding.
Theorems of Equal Angles: Two angles are said to be equal if they have equal measures.
90
3 and 6 ,4 and 5 Alternate Interior. 1 and 8 ,2 and 7 Alternate Exterior.
4 and 6 ,3 and 5 Interior. 1 and 7 ,2 and 8 Exterior.
1 and 5 ,2 and 6,3 and 7,4 and 8 Corresponding.
1. Vertical angles are equal.
Vertical Angles
91
3 and 6 ,4 and 5 Alternate Interior. 1 and 8 ,2 and 7 Alternate Exterior.
4 and 6 ,3 and 5 Interior. 1 and 7 ,2 and 8 Exterior.
1 and 5 ,2 and 6,3 and 7,4 and 8 Corresponding.
1. Vertical angles are equal.2. Alternate Interior, alternate exterior, corresponding Angles are equal.
Vertical Angles
92
1. Vertical angles are equal.2. Alternate Interior, alternate exterior, corresponding Angles are equal.3. If the right and left sides of two angles are parallel to each other, the angles are equal.
1
2
93
1. Vertical angles are equal.2. Alternate Interior, alternate exterior, corresponding Angles are equal.3. If the right and left sides of two angles are parallel to each other, the angles are equal.3. If the right and left sides of two angles are perpendicular to each other, the angles are equal.
1
2
94
1
Central AngleCentral Angle
Inscribed AngleInscribed Angle
2
1
C
2
95
TRIANGLESTRIANGLES
96
TRIANGLESTRIANGLES
Triangle - Formed by three line segments called sides.Vertex – point common to two sides.Altitude – Perpendicular line segment drawn from any vertex to opposing side.
Base
97
TRIANGLES – Right TriangleTRIANGLES – Right Triangle
Leg
Leg
Hypotenuse
98
TRIANGLESTRIANGLES
Scalene – no two sides are of equal length.Acute – each angle less than 90 degrees.Obtuse – one angle greater than 90 degrees.Right – One angle equals 90 degrees.
99
TRIANGLESTRIANGLES
Isosceles – Two of the sides are equal.Acute – each angle less than 90 degrees.Obtuse – one angle greater than 90 degrees.Right – One angle equals 90 degrees.
100
Congruence of TRIANGLESCongruence of TRIANGLES
If two triangles can be made to coincide by superposition, they are said to be congruent.
A
B
C
A'
B'
C'
101
Congruence of TRIANGLESCongruence of TRIANGLES
A
B
C
A'
B'
C' ABC≈ A' B ' C '
102
Congruence of TRIANGLESCongruence of TRIANGLES
A
B
C
A'
B'
C' ABC≈ A' B ' C '
1.) AB=A' B ' BC=B ' C ' B=B '
2.)A=A ' C=C ' AC=A' C '
3.) AB=A' B ' BC=B ' C ' AC=A' C '
B
A C B 'A '
C '
103
Similarity of TRIANGLESSimilarity of TRIANGLES
A
B
C
A'
B'
C'B
A C
A ' C '
B '
Dimensions of one are a constant ratio of the other.
ABC ~ A' B ' C '
104
Similarity of TRIANGLESSimilarity of TRIANGLES
A
B
C
A'
B'
C'
ABC ~ A' B ' C '
1.)A=A ' B=B '2.) AB /AC=A' B ' /A' C ' A=A'
3.) AB / A' B '=AC / A' C '=BC /B ' C '4.)A=A ' B=B ' C=C '5.) Their corresponding sides are respectively parallel or perpendiculiar.
B
A C
A ' C '
B '
105
Similarity of TRIANGLESSimilarity of TRIANGLES
A
B
C
A'
B'
C'
ABC ~ A' B ' C '
6.) The hypotenuse and a leg of one are respectively proportional to the hypotenuse and a leg of the other .7.) An acute angle of one is equal to an acute angleof the other.
B
A=90o C
A '=90o C '
B '
hyp
hyp'
106
Other Theorems of TRIANGLESOther Theorems of TRIANGLES
A
B
C
1.) Sum of the angles of every triangles is 180o .
2.) Sum of any two sides is greater than third,difference of any two sides is less than the third
3.) Angles opposite equal sides are equal, and conversely.
4.) The largest angle in a triangle lies opposite the largestand conversely.
B
A C
107
Other Theorems of TRIANGLESOther Theorems of TRIANGLES
A
B
C
5.) Line parallel to one side of a triangle divides the other two sides into proportional segments.
AD /DB=AE /EC
B
A C A
B
C
B
A C
D
E
108
AB=30m
AC=?
A B
C
109
AB=30m
AC=?
A B , B '
C
C '
A'
DE=2m
A' B '=5m
Similar Triangles
110
AB=30m
AC=?
A B , B '
C
C '
A'
DE=2m
A' B '=5m
Similar Triangles
111
AB=30m
AC=?
A B , B '
C
C '
A'
DE=2m
A' B '=5m
Similar Triangles
112
AB=30m
AC=?
A B , B '
C
C '
A'
A' C '=2m
A' B '=5mACAB
= A' C 'A' B '
113
AB=30m
AC=?
A B , B '
C
C '
A'
A' C '=2m
A' B '=5mACAB
= A' C 'A' B '
AC=AB[ A' C 'A ' B ' ]=30m[ 2m5m ]=12m
114
m
115
m
w=mg
Dotted line drawn perpendicular to ramp.
116
m
w=mg
90o−
Dotted line drawn perpendicular to ramp.
117
m
w=mg
90o−
Dotted line drawn perpendicular to ramp.
118
m
w=mg
90o−
Normal x,y coordinate system.
F N
119
m
w=mg
90o−
Normal x,y coordinate system.
F N
120
m
w=mg
90o−
Normal x,y coordinate system.
F N
90o−
121
m
w=mg
90o−
Normal x,y coordinate system.
F N
90o−
122
123
124
125
126
Pythagorean TheoremPythagorean Theorem
r2=x2 y2
r
xy
127
Pythagorean TheoremPythagorean Theorem
r2=x2 y2
r=x2 y2
r=3m 24m 2=5m
r=?
x=3my=4m
128
Quadrilaterals:Quadrilaterals:Quadrilateral – plane figure bounded by four line segments.
Parallelogram – opposite sides are parallel.
Trapezoid – Only one pair of parallel opposite sides.
Rhombus – parallelogram with all sides being equal.
Rectangle – parallelogram with four right angles.
Square – rectangle with four equal sides.
129
Quadrilaterals:Quadrilaterals:Quadrilateral – plane figure bounded by four line segments.Parallelogram – opposite sides are parallel.Trapezoid – Only one pair of parallel opposite sides.Rhombus – parallelogram with all sides being equal.Rectangle – parallelogram with four right angles.Square – rectangle with four equal sides.
Rectangle Square Parallelogram
Rhombus Trapezoid
130
Quadrilaterals:Quadrilaterals:A Quadrilateral is a parallelogram if any of the following:
1.) Two sides are equal and parallel.
2.) Each interior angle is equal to the interior opposite angle.
3.) Diagonals bisect one another.
4.) Opposite sides are equal in length.
131
Parallelogram:Parallelogram:A diagonal of a parallelogram divides it into two congruent triangles.
Two angles with a common side in a parallelogram are supplementary.
The measure of the sum of the four angles is:180 o + 180 o = 360 o .
A
A A
132
Parallelogram:Parallelogram:Special Properties:
1.) Rhombus - diagonals are perpendicular
2.)Rhombus – diagonals bisect angles.
3.)Rectangle – square of the length of the diagonal is equal to sum of the square of the lengths of the two adjacent sides.
4.) Rectangle – two diagonals are equal.
5.) A square ( parallelogram, rhombus, rectangle) has all properties listed.
133
Circles and ArcsCircles and Arcs
Diameter
Radius
134
Circles and ArcsCircles and Arcs
SecantSecant
TangentTangent
ChordChord
135
Circles and ArcsCircles and Arcs
Sector
Arc
Semicircle
Quadrant
136
sagitta
137
An inscribed angle is measured by one-half if the intercepted arc.
138
An inscribed angle is measured by one-half if the intercepted arc.
Arc 1/3 of circle, or 13 360o=130o
=130o
2=65o
139