The Cosine Addition Formulas - Concept

Concept Concept (1)

The cosine addition formula calculates the cosine of an angle that is either the sum or difference of two other angles. It arises from the law of cosines and the distance formula. By using the cosine addition formula, the cosine of both the sum and difference of two angles can be found with the two angles' sines and cosines.

Sample Sample Problems (3)

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The Cosine Addition Formulas - Problem 1
Problem 1
How to use the cosine of a difference formula to simplify an expression or to find the cosine of an angle.
The Cosine Addition Formulas - Problem 2
Problem 2
How to derive the cosine of a sum formula and use it to find the cosine of an angle.
The Cosine Addition Formulas - Problem 3
Problem 3
How to evaluate cos(a - b) and cos(a + b) when you know only sin(a) and cos(b).