Calculating an angle The three trigonometric ratios can be used to calculate the size of an angle in a right-angled triangle.

Two New Orleans high school students have proven the Pythagorean Theorem using trigonometry without relying on circular reasoning. That should be impossible.

National 5 Maths - Calculating the area of a triangle using trigonometry Revise how to calculate the area of a non right-angled triangle as part of National 5 Maths.