Trigonometry 
| Pythagorean Identities sin2 θ + cos2 θ = 1 tan2 θ + 1 = sec2 θ cot2 θ + 1 = csc2 θ |
| Ratio Identities  | ||||||||
| Odd/Even Identities | |
| sin (–x) = –sin x cos (–x) = cos x tan (–x) = –tan x | csc (–x) = –csc x sec (–x) = sec 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 | Periodicity Identities, degrees | |||
| sin (x + 2π) = sin x | 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 | cot (x + π) = cot x | tan (x + 180°) = tan x | sin (x + 180°) = cot x | |
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| Half Angle Identities |
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SOURCE :INTERNET
