Question

Cho AOB. Trong AOB ve OC, OD sao cho OC vuong goc OA, OB vuong goc OD. Tinh COD

Answer 1

Đặt \(\widehat{AOB}=\alpha\)\(\left(0^o< \alpha< 90^o\right)\)

Ta có \(\widehat{AOB}+\widehat{BOC}=\alpha+\widehat{BOC}=\widehat{AOC}=90^o\)

=> \(\widehat{BOC}=90^o-\alpha\)(1)

và \(\widehat{BOC}+\widehat{COD}=90^o\)

=> \(\widehat{BOC}=90^o-\widehat{COD}\)(2)

Từ (1) và (2)

=> \(\widehat{AOB}=\widehat{COD}=\alpha\)