Angles in a triangle add up to 180° and quadrilaterals add up to 360°. Angles can be calculated inside semicircles and circles, as well as with perpendicular bisectors and tangents.

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This section deals with 2D shapes and angles related to them. It might be worth looking at the National 4 Angles section before continuing.

For any triangle, the three angles add up to .

Find the value of in the triangle below.

An equilateral triangle is one with all three sides equal in length and all three angles equal to .

An isosceles triangle is one with two sides equal in length and two equal angles.

- Question
In this diagram, the triangle is isosceles so both base angles equal .

What is the value of ?