The height of an isosceles triangle can also be found using Pythagoras’ theorem. Consider a triangle with base x and two equal sides measuring y: We can bisect the triangle, or split it into two equal parts. This is shown by the dotted line which will meet the base at a right angle. By doing this, we create two right-angled triangles! The base of one will be (x ÷ 2) and the hypotenuse will be y. We can use these to find the height of the isosceles triangle.