Trigonometric Functions

A radian is the angle subtended

A radian is the angle subtended at the center of a circle by an arc equal in length to the radius. The relationship between degrees and radians: 180°

For a point P(x

For a point P(x,y) on the unit circle corresponding to angle θ: sin θ = y-coordinate, cos θ = x-coordinate, tan θ = y/x (x≠0). Domain and range: sin θ

Sin and cos functions

Sin and cos functions: periodic with period 2π, continuous everywhere, oscillating between -1 and 1. Tan and cot functions: periodic with period π, di

cos(A ± B) = cos

cos(A ± B) = cos A cos B ∓ sin A sin B; sin(A ± B) = sin A cos B ± cos A sin B; tan(A ± B) = (tan A ± tan B)/(1 ∓ tan A tan B). Example: sin(75°) = si

Double angles

Double angles: sin 2A = 2 sin A cos A; cos 2A = cos²A - sin²A = 2cos²A - 1 = 1 - 2sin²A; tan 2A = 2 tan A/(1 - tan²A). Triple angles: sin 3A = 3 sin A