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Angles Inscribed in a Semicircle

An angle is inscribed in a circle when it is created by chords and the vertex is on the circumference of the circle. When the chords have endpoints on the diameter, it is inscribed in a semicircle. Angle APB is inscribed in a semicircle. You can drag point A to change the orientation of the semicircle.

Drag P along the circle.

What do you notice about angle APB?

Change the size of the circle by using the slider to change the radius.

Does the measure of APB change when the circle is a different size?

Complete the statement below based on your observations.

An angle inscribed in a semi-circle ________