Angles Study Notes | Maths Learn & Test

There are 3 main types of angle: Right Angles are 90° (note the symbol used to show a Right Angle) Acute Angles are < 90° Obtuse Angles are > 90°

There are also some key rules to learn about angles.

Angles on a straight line add up to 180° a + b + c = 180°

Angles around a point add up to 360° a + b + c + d + e = 360°

Angles in a triangle add up to 180° a + b + c = 180°

There are a couple of special triangles too.

In an equilateral triangle, all the angles are 60°

The angles between each equal side and the unequal side in an isosceles triangle are the same.

You only need to know one angle in an isosceles triangle to be able to work out the other two.

Angles in a quadrilateral add up to 360° a + b + c + d = 360°

Three angles in a quadrilateral are 70°, 120° and 84°. What is the fourth angle?

The sum of the angles of a quadrilateral is 360° so the missing angle is: 360° - (70° + 120° + 84°) = 86°