Pre-calculus question
Can someone help me with the calculation part of this question:
1. Derive this identity from the sum and difference formulas for cosine:
cos a cos b = (1 / 2)[cos(a – b) +cos(a + b)]
Calculation
Reason
-This follows from the sum and difference formulas for cosine.
-This follows from algebraic simplification.
This proves the identity:

Question

Pre-calculus question
Can someone help me with the calculation part of this question:
1. Derive this identity from the sum and difference formulas for cosine:
cos a cos b = (1 / 2)[cos(a – b) +cos(a + b)]
Calculation	
Reason
-This follows from the sum and difference formulas for cosine.
-This follows from algebraic simplification.
This proves the identity:

phi · Answer

do you know the sum and difference formulas for cosine ?