Question
The angle inscribed in the semicircle is a right angle. Prove the result by completing the following activity.

Given: $\angle A B C$ is inscribed angle in a semicircle with center $M$
To prove: $\angle A B C$ is a right angle.
Proof: Segment AC is a diameter of the circle.
$
\therefore m(\operatorname{arc} A X C)=\square
$
Arc $A X C$ is intercepted by the inscribed angle $\angle A B C$
$\angle ABC =\square$ [Inscribed angle theorem]
$
=\frac{1}{2} \times \square
$
$\therefore m \angle ABC =\square$
$\therefore \angle ABC$ is a right angle.

Answer

Proof: Segment AC is a diameter of the circle.
$
\therefore \operatorname{m}(\operatorname{arc} AXC )=180^{\circ}
$
...(i) [Measure of semi circular arc is $180^{\circ}$ ]
Arc AXC is intercepted by the inscribed angle $\angle A B C$
$
\angle ABC =\frac{1}{2} m (\operatorname{arc} AXC )
$
[Inscribed angle theorem]
$
=\frac{1}{2} \times 180^{\circ}
$
[From (i)]
$
\therefore m \angle ABC =90^{\circ}
$
$\therefore \angle A B C$ is a right angle.

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