**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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