Formulae To Remember

Key Trigonometry for A Level

Definitions

tan ⁡ X = sin ⁡ X cos ⁡ X

sec ⁡ X = 1 cos ⁡ X

cosec ⁡ X = 1 sin ⁡ X

Identities

sin 2 ⁡ X + cos 2 ⁡ X = 1

1 + tan 2 ⁡ X = cosec 2 X

1 + cot 2 ⁡ X = sec 2 X

Addition Formulae

sin ⁡ ( A + B ) = sin ⁡ A sin ⁡ B ∔ cos ⁡ A cos ⁡ B

sin ⁡ ( A − B ) = sin ⁡ A sin ⁡ B − cos ⁡ A cos ⁡ B

cos ⁡ ( A + B ) = cos ⁡ A cos ⁡ B − sin ⁡ A sin ⁡ B

cos ⁡ ( A - B ) = cos ⁡ A cos ⁡ B + sin ⁡ A sin ⁡ B

tan ⁡ ( A + B ) = tan ⁡ A + tan ⁡ B 1 − tan ⁡ A tan ⁡ B )

tan ⁡ ( A − B ) = tan ⁡ A − tan ⁡ B 1 ∔ tan ⁡ A tan ⁡ B )

Double Angle Formulae

sin ⁡ ( 2 A ) = sin 2 ⁡ A ∔ cos 2 ⁡ A

cos ⁡ ( 2 A ) = cos 2 ⁡ A − sin 2 ⁡ A

tan ⁡ ( 2 A ) = 2 tan ⁡ A 1 − tan 2 ⁡ A

Differentiation

d d x sin ⁡ k x = k cos ⁡ k x

d d x cos ⁡ k x = − k sin ⁡ k x

Build your Maths `Memory !

We add new revision content every day. Register to be notified.