The isosceles triangle can be split into two right-angled triangles. Pythagoras’ theorem can then be used on either of the two right-angled triangles. The 25 cm length becomes the hypotenuse so ...

The converse of the theorem says that if, \({a^2} = {b^2} + {c^2}\) then you have a right-angled triangle and furthermore, the right angle is directly opposite \(a\) (the hypotenuse). We can ...