Angle subtended in a semi-circle by the largest chord of a circle is

 

Concept: A chord is a straight line whose ends are on the circle's circumference. A diameter is the longest chord that can be formed.

Let  $AB$ be the diameter.

We can say that the angle subtended by a chord at centre is twice the angle subtended by that chord at any point on the circumference.

Angle subtended by $AB$ at centre $O$ is  ${180}^0$.

So, it follows that the angle in a semicircle is always a right angle.

Hence, an angle subtended in a semi-circle by the largest chord of a circle is right angle.