Lines AB and CD intersect at a point O in such a way that ∠DOB = 4∠COB. What is ∠AOD?
In 4ABC, AB = AC and ∠A = 72◦ . What is ∠B?
O is the circumcenter of 4ABC. If OB = OC = BC, what is ∠BAC?
Lines AB and CD intersect at a point O in such a way that ∠DOB = 4∠COB. What is ∠AOD?
A C
O
D B
DOB + COB =180
Then
4COB + COB =180
5COB =180
COB = 180/5 = 36
And AOD is the vertical angle to COB......so AOD also = 36 (degrees)