Question

$O$ is the centre of the circle, Find $\angle CBD$

Answer 1

As $OABC$ is a cyclic quadrilateral , sum of opposite angles is ${180}^o$

$\Rightarrow \angle AOC+\angle ABC={180}^o\Rightarrow \angle ABC=180-115={65}^o$

BY linear angle property, $\angle ABC+\angle CBD={180}^o$

$\Rightarrow \angle CBD=180-65={115}^o$