Question

Please help me with this question

Answer 1

`\overline{\sf COB}` is the diameter of circle O.

The angle on a straight line is 180° ⇒ ∠COB = 180°

The angle at the center of a circle is twice the angle at the circumference:

⇒ ∠CAB = 1/2 of ∠COB = 1/2 x 180°

⇒ ∠CAB = 90°

Answer 2

Explanation:

Insribed angle is half the measure of intercepted arc.

• m∠CAB = 1/2mCDB

Since O is the center COB is the diameter of this circle.

The diameter splits the circle into two equal arcs. As the full circle is 360°, each semicircle is 180°.

So

• 1/2mCDB = 1/2(180°) = 90°

And the angle measure is

• m∠CAB = 90

Proved