91Ó°ÊÓ

The provided figure represents two equal angles which are $∠ABD$and $∠CBD$which are the parts of angle $∠AOC$. The value of angle $∠ABD$is represented by $88°$.

As the$∠AOC$ represents itself as a straight angle so the addition of both the angles $∠ABD$and $∠CBD$will be equal to $180°$.

Make an equation by taking the addition of the angles $∠ABD$and $∠CBD$equal to $180°$.

$$\begin{gathered} m∠CBD+m∠ABD=180° \\ m∠CBD+88°=180° \\ m∠CBD=180°−88° \\ m∠CBD=92° \end{gathered}$$

The provided figure represents two equal angles which are $∠ABD$and $∠CBD$which are the parts of angle $∠AOC$. The value of angle $∠ABD$is represented by $88°$.

As the$∠AOC$ represents itself as a straight angle so the addition of both the angles $∠ABD$and $∠CBD$will be equal to $180°$.

The postulate 4 satisfies the answer of part (a) because postulate 4 states that if an angle represents itself as a straight angle so the addition of angles that are present in that angle will be equal to $180°$.