Original post by eraine
a) show that cos 7x + cos 3x = 2 cos 5x cos 2x by expanding cos(5x+2x) and cos(5x-2x) using the compound angle formulas
b) hence find integral (cos5x cos 2x).dx
b) hence find integral (cos5x cos 2x).dx
Do you know the compound angle formulas for cos?
Original post by eraine
Yes......cos (A + B) = cos A cos B - sin A sin B
So use it.
Add these together, simplify, then thats it.
is this GCSE? :x
Original post by SmartUnicorn
is this GCSE? :x
No.
Quick Reply
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