triangle

a three sided closed polygon

A

G B

symbolic notation:∆BAG

acute angle

an angle whose measure is less than 90ᴼ

40ᴼ AWWW… Such a CUTE little angle!

symbolic notation:m∠A = 40ᴼ

A

right angle

an angle whose measure is exactly 90ᴼ

symbolic notation:m∠B = 90ᴼ

B

obtuse angle

an angle whose measure is greater than 90ᴼ

symbolic notation:m∠C = 120ᴼ

C120ᴼ

(obtuse angle)

straight angle

an angle whose measure is exactly 180ᴼ

symbolic notation:m∠ABC = 180ᴼ

BA C

HINT: THERE IS ONLY 1 STRAIGHT ANGLE…(thus a straight angle is different from supplementary angles!!!)

congruent

Two figures, segments, triangles, etc. that have the same size, same shape, same measure

∆PQR ≅ ∆LJK

symbolic notation:≅

C’B’

A’

A

B

C

Example of a Rule for a

Transformation:(x,y)→‘(-y,x)

imagepre-image

collineara set of points that lie on the same line

example:

Points P, Q, & R are collinear. Points X, Y, & Z are noncollinear.

symbolic notation:P, Q, and R,are collinear

symbolic notation:⊥

symbolic notation:∥

no symbolic notation

dilation

a transformation that results in similar figures

AB

Figure A has been dilated by a scale factor of 2 to form Figure B.

Intersecting Lines

• Two lines that cross at a single point.

• Symbolic Notation: none

Polygon

• A closed figure in a plane with at least three straight sides

• Symbolic Notation: none

Regular V. Irregular Polygon

• Regular polygons have all congruent sides and interior angles.

• Irregular polygons do not have all congruent sides and interior angles.

• Symbolic Notation: None