Answer
When an angle is inscribed in a circle, its value is equal to half of the value of the arc that intersects it. Since the circle is a semicircle, its angle is half of that of a regular circle, meaning that its angle is half of 360 degrees (which is 180 degrees). Since when an angle is inscribed in a circle, its value is equal to half of the value of the arc that intersects it, it follows that the inscribed angle is equal to 90 degrees, which is a right angle.
