Trigonometry

In a right

In a right-angled triangle, the side opposite the right angle is the hypotenuse. For a chosen acute angle, the side opposite that angle is the opposit

For an acute angle A

For an acute angle A in a right-angled triangle, sin A = BC/AC, cos A = AB/AC, and tan A = BC/AB.

cosec A = 1/sin

cosec A = 1/sin A, sec A = 1/cos A, and cot A = 1/tan A.

tan A = sin A /

tan A = sin A / cos A. This links the three primary ratios and is often used in simplification.

cos^2 A + sin^2 A =

cos^2 A + sin^2 A = 1. It comes from the Pythagorean theorem applied to a right triangle.