trig identities

sin = SCCS (same sign) cos = CCSS (diff. sign)

Pythagorean Identities (Main Identity)

cos²x + sin²x = 1

Pythagorean Identities (In terms of tan x)

**divide by cos

1 + tan²x = sec²x

Pythagorean Identities (In terms of cos x)

**divide by sin

1 + cot²x = csc²x

Sin sum Identity

sin(a + B) = sin a cos B + cos a sin B

Cos sum identity

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

Sin difference identity

sin ( a - B) = sin a cos B - cos a sin B

cos difference identities

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

sin double agent identities

sin(2b) = 2sin b cos b

cos double agent identities

cos(2b) = cos²b - sin²b OR

1 - 2 sin²b OR

2cos²b - 1