Angle APB = 90°
Calculate the angle .
The angle at the circumference in a semicircle is 90°.
Angle STU = 90°
Angles in a triangle add up to 180°.
The angle on a straight line is 180°. The angle VOY = 180°.
The angle at the centre is double the angle at the circumference.
Angle VWY = of angle VOY = .
Angle VWY = 90°