Sum and Difference Identities
In trigonometry, there are six sum and difference identities. They are useful when the given angle in a trigonometry expression cannot be evaluated. The six sum and difference identities are given as:
Evaluate the following trigonometry expressions by using the sum and difference identities.
To evaluate the angle without a calculator we can use – .
This means we use the difference identities where a – b = – . Therefore, a = and b = .
The final answer is or 0.259.
The final answer is or 0.966.
The final answer is or 0.268.