8/25/2017
Mathwords: Trig Identities
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Trig Identities
Identities involving trig functions are listed below.
Pythagorean Identities
Ratio Identities
Reciprocal Identities
sin2 θ + cos2 θ = 1
tan2 θ + 1 = sec2 θ
index: subject areas
numbers & symbols
cot2 θ + 1 = csc2 θ
sets, logic, proofs
geometry
algebra
trigonometry
advanced algebra
& pre-calculus
Odd/Even Identities
calculus
advanced topics
probability &
statistics
real world
applications
multimedia
entries
sin (–x) = –sin x
csc (–x) = –csc x
cos (–x) = cos x
sec (–x) = sec x
tan (–x) = –tan x
cot (–x) = –cot x
Cofunction Identities, radians
Cofunction Identities, degrees
sin (90° – x) = cos x cos (90° – x) = sin x
tan (90° – x) = cot x cot (90° – x) = tan x
sec (90° – x) = csc x csc (90° – x) = sec x
Periodicity Identities, radians
sin (x + 2π) = sin x
Periodicity Identities, degrees
csc (x + 2π) = csc x
sin (x + 360°) = sin x
csc (x + 360°) = csc x
cos (x + 2π) = cos x sec (x + 2π) = sec x
cos (x + 360°) = cos x sec (x + 360°) = sec x
tan (x + π) = tan x
tan (x + 180°) = tan x cot (x + 180°) = cot x
cot (x + π) = cot x
Sum/Difference Identities
Double Angle Identities
Half Angle Identities
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8/25/2017
Mathwords: Trig Identities
or
or
or
Product to Sum Identities
or
Sum to Product Identities
See also
Sine, cosine, tangent, cosecant, secant, cotangent
this page updated 19-jul-17
Mathwords: Terms and Formulas from Algebra I to Calculus
written, illustrated, and webmastered by Bruce Simmons
Copyright © 2000 by Bruce Simmons
All rights reserved
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