Trig Formulas

Second Half of First

cos(2θ) is equivalent to:

cos²(θ) - sin²(θ)

sin(2θ) is equivalent to:

2sin(θ)cos(θ)

tan(2θ) is equivalent to:

2tan(θ)/1 - tan²(θ)

sin + cos cofunction identities

sin(π/90 - θ) = cosθ
cos(π/90 - θ) = sinθ

csc + sec cofunction identities

csc(π/90 - θ) = secθ
sec(π/90 - θ) = cscθ

tan + cot cofunction identities

tan(π/90 - θ) = cotθ
cot(π/90 - θ) = tanθ

cos odd/even function

cos(-θ) = cosθ

sin odd/even function

sin(-θ) = -sinθ

csc odd/even function

csc(-θ) = -cscθ

sec odd/even function

sec(-θ) = secθ

tan odd/even function

tan(-θ) = -tanθ

cot odd/even function

cot(-θ) = -cotθ

sine sum formula

sin(A + B) = sinA cosB + cosA sinB

sine difference formula

sin(A - B) = sinA cosB - cosA sinB

cosine sum formula

cos(A + B) = cosAcosB - sinAsinB

cosine difference formula

cos(A - B) = cosAcosB + sinAsinB