4) Angles in a semicircle
The angle at the circumference in a semicircle is a right angle.
Angle APB = 90°
Calculate the angle z.
The angle at the circumference in a semi-circle is 90°.
Angle STU = 90°
Angles in a triangle add up to 180°.
z = 180° – 90° – 31° = 59°
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 = 1/2 of angle VOY = 1/2 x 180°.
Angle VWY = 90°