SOLUTION: Verify, ' cosxcosy = 1/2 [cos(x+y) + cos(x-y)] ' My professor did not properly explain this. I don't understand how to solve the equation. ' Thank You

Question 513387: Verify,
'
cosxcosy = 1/2 [cos(x+y) + cos(x-y)]
'
My professor did not properly explain this. I don't understand how to solve the equation.
'
Thank You
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
verify:
cosxcosy = 1/2 [cos(x+y) + cos(x-y)]
starting from right side:
using addition formulas
1/2[(cosxcosy-sinxsiny)+((cosxcosy+sinxsiny)]
=1/2(2cosxcosy)=cosxcosy
verified:
right side = left side
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