Trigonometric Identities

Question 1

Sine Compound Angle Formulae

Answer 1

sin(A_+_B) = sinAcosB + cosAsinB
‘+’ leads to ‘+’

Question 2

Cosine Compound Angle Formulae

Answer 2

cos(A_+_B) = cosAcosB + sinAsinB
‘+’ leads to ‘-‘

Question 3

Tangent Compound Angle Formulae

Answer 3

tan(A_+_B) = tanA + tanB / 1 + tanAtanB
Numerator: ‘+’ leads to ‘+’
Denominator: ‘+’ leads to ‘-‘

Question 4

Sine Double Angle Formulae

Answer 4

sin2x = 2sinxcosx

Question 5

Cosine Double Angle Formulae

Answer 5

cos2x = cos²x - sin^wx
= 2cos²x - 1
= 1 - 2sin²x

Question 6

Tangent Double Angle Formulae

Answer 6

tan2x = 2tanx / 1 - tan²x