Question 1154876
*[illustration central.png].
Central angle = Angle subtended by an arc of the circle from the center of the circle.
Inscribed angle = Angle subtended by an arc of the circle from any point on the circumference of the circle.

inscribed angle = 1/2 central angle.

Diameter is a semi circle. It subtends 180 deg

so angle ACB will always be  90 deg. wherever C is located