Trigonometric substitution

Trigonometric substitution is a way we can use maths to figure out the area of a shape that isn't a normal rectangle or square. To do this, we use something called trigonometry. Trigonometry is a type of math that helps us measure sides and angles of triangles. So, in order to figure out the area of a shape, we have to figure out the area of a triangle first. To do this, we use trigonometric substitution. With this, we can substitute a trigonometric function for a side of the triangle and use that to figure out the area.