Some useful references on Trigonometry:

Basic Trigonometric Identities:

Compound Angle Relations:

Product To Sum Formula:

Double Angle Formulae:

Factor Formulae:

Some Extra Things:

R-Formula:

a cos θ ± b sin θ = R cos (θ ∓ α)
 
a sin θ ± b cos θ = R sin (θ ± α)
,where
$R = \sqrt{a^{2}+b{2}}$ and,
$tan \alpha = \frac{b}{a}$ and,
and a > 0, b > 0, α is acute

Note: 
The maximum value is R which occurs when cos/sin (θ ± α) = 1
The minimum value is -R which occurs when cos/sin (θ ± α) = -1

Even/Odd Functions

Cofunction Identities

 

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