Jay Holland and Sonny Soto
The Trigonometric Identities for PreCalculus
Trigonometry Identities
Reciprocal Identities
sinθ=(1/cscθ)
cosθ=(1/secθ)
tanθ=(1/cotθ)
cscθ=(1/sinθ)=(h/y)
secθ=(1/cosθ)=(h/x)
cotθ=(1/tanθ)=(cosθ/sinθ)=(x/y)
Pythagorean Identities
Product Identities
sinθ=tanθ(coxθ)
cosθ=cotθ(sinθ)
tanθ=sinθ(secθ)
cscθ=cotθ(secθ)
secθ=tanθ(cscθ)
cotθ=cosθ(cscθ)
Quotient Identities
sinθ=(tanθ/secθ)
cosθ=(cotθ/cscθ)
tanθ=(sinθ/cosθ)
cscθ=(cotθ/cosθ)
secθ=(tanθ/secθ)
cotθ=(cosθ/sinθ)
Cofunction Identities
sinθ=cos((π/2)-x)
cosθ=sin((π/2)-x)
Even and Odd Identities
sin(-θ)=-sinθ
cos(-θ)=-cosθ
tan(-θ)=-tanθ
csc(-θ)=-cscθ
sec(-θ)=-secθ
cot(-θ)=-cotθ