For a right-angled triangle, follow these steps to calculate the length of a side, \(x\), when another side and an angle Ɵ is given: Formula triangles ... be labelled as hypotenuse (\(h\)).

When labelling a length as the hypotenuse ... but it might not be. To find out if it is a right-angled triangle check if Pythagoras’ theorem is true for the lengths of the sides.