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KIM TRA BI C Cho tia Ox. Trn cng mt na mt phng b cha tia Ox, v tia Oy, Oz sao cho xOy = 1200, xOz = 600 a) Trong ba tia Ox, Oy, Oz tia no nm gia hai tia cn li? b) Tnh yOz ? c) So snh xOz v yOz ? Bi gii a) Trn cng mt na mt phng z b cha tia Ox, c: y xOz < xOy ( 600 < 1200) Tia Oz nm gia hai tia Ox v Oy. b) xOz + zOy = xOy 600 + zOy = 1200 zOy = 1200 - 600 zOy = 600 c) xOz = zOy (= 600)
1200 600
O
x
x
O
z
Tia phn gic ca mt gc l tia nm gia hai cnh ca gc v to vi hai cnh y hai gc bng nhau
y
Khm ph:Mt s hnh nh thc t v tia phn gic ca mt gc?
1.
Khi cn thng bng th kim trng vi tia phn gic ca gc AOB
O
B
t
A
Mun qu cu A khi c y vo im O trn cnh bn khi bn ra trng qu cu B th phi xc nh im O sao cho tia Ot (vung gc vi cnh bn ti O) l tia phn gic ca gc AOB.
Da vo nh ngha, cho bit tia no l tia phn gic ca gc trong cc hnh v sau. V sao?b n a O O B
mO
A
pc
C
Oa khng l tia Om khng l tia phn phn gic ca bOc gic ca nOp v tia Om khng nm gia v aOb aOc tia On v tia Op
OA l tia phn gic ca BOC v OA nm gia OB v OC AOB = AOC
V d: V tia phn gic Oz ca gc xOy c s o 640 Do Oz tia l phn gic ca gc xOyTa c: xOz = zOy M xOz + zOy = 640 640 = 320 Suy ra xOz = 2
Cch v:- V xOy = 640 - V tia Oz nm gia 2 tia Ox v Oy sao y cho xOz = 320
zo
32
64o
o
32
O
x
Gp giy:32 640 0
320
V gc xOy ln giy.Gp giy sao cho cnh Ox trng vi cnh Oy
Np gp cho ta v tr ca tia phn gic. V tia phn gic theo np gp .
O
m t x a Cac nhom thc hien gap giay nh sau: Nhom 1: Gap tia phn gic ca goc nhon t Nhom 2: Gap tia phno gic ca gc Vuong 45 Nhom 3: Gap tia phn gic ca goc tu n O O Nhom 4: Gap tia phn gic ca goc bet y
b
c
Hai tia Ot, Ot la tia phan giac cua goc bet xOy Goc bet co hai tia phan giac la hai tia oi nhau
t
x
O t
y
HOT NG NHM: THI GIAN 3 PHT
Hy v hnh theo cch din t sau:
- V gc bt xOy- Trn na mp phng b l ng thng xy, v tia Oz sao cho gc xOz = 500 - V tia phn gic On ca gc xOz
- V tia phn gic Om ca gc yOz
x
m
O m n x O y
y
n
ng thng mn l ng phn gic ca xOy
Bt 32/87 Sgk: Khi no ta kt lun c tia Ot l tia phn gic ca gc xOy? Chn cu ng trong cc cu sau: Ot l tia phn gic ca gc xOy khi: a) xOt = yOt. b) xOt + tOy = xOy. c) xOt + tOy = xOy v xOt = yOt. xOy d) xOt = yOt = 2 Din t tia phn gic ca gc bng cc cch khc nhau? Oz l tia phn gic ca xOy Oz nm gia Ox, Oy xOz = zOy xOy xOz = zOy = 2
C TH EM CHA BIT ?CC CCH V TIA PHN GIC CA MT GC: 1. BNG KE:yz
O1 2 3
x 4 5 6
2/ BNG COM PA:
O1 2 y
z xBack
Bt 33/87/sgk: V hai gc k b xOy, yOx bit xOy = 1300. Gi Ot l tia phn gic ca gc xOy. Tnh xOt. Gii t Ot l tia phn gic ca gc xOy y xOy xOt = tOy = 2 130 1300 ? xOt = tOy = 2 = 650 x x' O V Ot nm gia Ox, Oy nn xOy xOt + xOt = xOx xOt = tOy = 2 xOt = xOx- xOt xOt = 1800 650 xOy + yOt xOx xOt xOt = 1150 xOt = ?
DN D
Hc k nh ngha tia phn gic, ng phn gic ca mt gc. Bi tp v nh: 30 , 34, 35 trang 87 Sgk