PCA - Trig Identities

Reciprocal Identity - Sin

sin θ = 1/cscθ

Reciprocal Identity - Cos

cos θ = 1/ sec θ

Reciprocal Identity - Tan

tan θ = 1/ cot θ

Quotient Identity: Tan

tan θ = sin θ / cos θ

Quotient Identity: Cot

cot θ = cos θ / sin θ

Cofunction Identities: sin, cos

sin θ = cos (90* - θ)

sin θ = cos (pi/2 - θ)

sin/cos switchable

Cofunction Identities: tan, cot

tan θ = cot (90* - θ)

tan θ = cot (pi/2 - θ)

cot/tan switchable

Cofunction Identities: sec, csc

sec θ = csc (90* - θ)

sec θ = csc (pi/2 - θ)

sec/cscswitchable

Pythagorean Identity: sin/cos

sin² θ + cos² θ = 1

Pythagorean Identity: tan/sec

1 + tan² θ = sec² θ

divide by cos²θ

Pythagorean Identity: cot/csc

cot²θ + 1 = csc²θ

divide by sin²θ