Sum and Difference Identities

Trigonometric identities which show how to find the sine, cosine, or tangent of the sum or difference of two given angles.

Formulas:

The sum and difference identities include the trigonometry formulas of sin(x + y), cos(x - y), cot(x + y), etc.

• sin(x + y) = sin(x)cos(y) + cos(x)sin(y)

• cos(x + y) = cos(x)cos(y) - sin(x)sin(y)

• tan(x + y) = (tan x + tan y)/(1 - tan x • tan y)

• sin(x – y) = sin(x)cos(y) - cos(x)sin(y)

• cos(x – y) = cos(x)cos(y) + sin(x)sin(y)

• tan(x − y) = (tan x - tan y)/(1 + tan x • tan y)

Sample Problems:

Try solving the questions below!

Answers