Trig Identities

Pythagorean Identities

cos²+sin²=1

sin²=1-cos²

cos²-1=sin²

1+tan²=sec²

tan²-sec²=-1

tan²=sec²-1

1+cot²=csc²

cot²-csc²=-1

cot²=csc²-1

Sum and Difference Formulas

sin(a+b)=sin(a) cos(b) + sin(b) cos(a)

sin(a-b) = sin(a) cos(b) - sin(b) cos(a)

cos(a+b)=cos(a) cos(b) - sin(a) sin(b)

cos(a-b)=cos(a) cos(b) + sin(a) sin(b)

Double Angle Formula

cos(2x) = cos² - sin²

cos (2x) = 2 cos² - 1

cos (2x) = 1-2sin²

sin(2x) = 2sin cos