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![](https://rs.olm.vn/images/avt/0.png?1311)
a) Ta có : \(\hept{\begin{cases}\widehat{AOB}=90^o+\widehat{AOC}\\\widehat{COD}=90^o-\widehat{BOC}\end{cases}\Rightarrow\widehat{AOB}+\widehat{COD}=90^o+\widehat{AOC}+90^o-\widehat{BOC}=180^o\Rightarrowđpcm}\)
b) Ta có : \(\widehat{BOC}=\widehat{AOD}\) (cùng phụ nhau với \(\widehat{COD}\))
\(\Rightarrow\frac{\widehat{BOC}}{2}=\frac{\widehat{AOD}}{2}\Rightarrow\widehat{COM}=\widehat{AON}\) (phân giác On và On)
Lại có : \(\widehat{CON}+\widehat{AON}=90^o\Rightarrow\widehat{CON}+\widehat{COM}=90^o\) hay \(\widehat{mOn}=90^o\)
\(\Rightarrow Om\perp On\left(đpcm\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Vì OA vuông góc với Oc nên góc AOc=90 độ
Vì góc AOB là góc tù nên góc AOB>góc AOc
=> Tia Oc nằm giữa tia OA và tia OB
=> góc AOc+góc BOc= góc AOB (1)
Vì Od vuông góc với OB nên góc BOd = 90 độ
Vì góc AOB là góc tù nên góc AOB>góc BOd
=> Tia Od nằm giữa tia OA và tia OB
=> góc AOd + góc BOd= góc AOB (2)
Vì góc AOc=góc BOd=90 độ nên từ (1) và (2) suy ra : góc AOd= góc BOc
Vậy đpcm.
P/s: mình vẽ hình chưa được chính xác lắm !!
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:
Góc BOD + góc DOC = 1200
=> góc DOC = 1200 - góc BOD = 120o - 90o = 30o
Góc AOC + góc COB = 120o
=> góc COB = 120o - góc AOC= 120o - 90o = 300
mà Góc BOC + góc COD + góc DOA = 120o
=> góc COD = 120o - ( góc BOC + góc DOA) = 1200 - 600 = 600
Ta có:
Góc BOC = Góc AOD
=> \(\frac{1}{2}BOC=\frac{1}{2}AOD=\frac{30}{2}=15^o\)
hay góc nOC = góc mOD = 15o
mà góc nOm= góc nOC +góc mOD + góc COD = 15o +150 +600 = 90o
hay nO vuông góc với mO.
![](https://rs.olm.vn/images/avt/0.png?1311)
a/ Vì tia OC nằm giữa tia OA và OB
=>AOC+COB=AOB
=>90 + COB = 120
=>COB=30 độ
tương tự tính được góc COB=30 độ
Mà AOD+DOC+COB=AOB
=>30+DOC+30=120
=>DOC=60 độ
b/ Vì Om là tia phân giác của AOC
=> O1=O2=AOD/2=30/2=15 độ
tương tự tính được góc O4=O5=15 độ
Mà góc mOn = O2+DOC+O4=15+60+15=90 độ
=> Om vuông góc với On
Hình vẽ:
![](data:image/png;base64,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)
Lời giải:
Ta có:
$\widehat{AOD}+\widehat{DOC}=\widehat{AOC}=90^0$
$\widehat{BOC}+\widehat{DOC}=\widehat{BOD}=90^0$
$\Rightarrow \widehat{AOD}+\widehat{DOC}=\widehat{BOC}+\widehat{DOC}$
$\Rightarrow \widehat{AOD}=\widehat{BOC}$
$\