Each trigonometric function also has an inverse that can be used to find an angle from a ratio of sides. ... Shapes other than right triangles. Trigonometry isn’t limited to just right triangles.

I'm talking about trigonometry, of course: that bastion of angles and triangles that is essential to calculating velocity, momentum, and much more.

Learn how to find the angles in right-angled triangles with this BBC Bitesize Maths article. For students between the ages of 11 and 14.