# Triangles

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 $$180^\circ$$.

### Example

Find the value of $$x^\circ$$ in the triangle below.

$x^\circ=180^\circ-(70^\circ+50^\circ)=180^\circ-120^\circ=60^\circ$

An equilateral triangle is one with all three sides equal in length and all three angles equal to $$60^\circ$$.

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 $$70^\circ$$.

What is the value of $$a^\circ$$?

$a^\circ=180^\circ-(70^\circ+70^\circ)=180^\circ-140^\circ=40^\circ$