Question

Question Below :)

Answer 1

Express cos7mcos3m as a sum or difference

Answer 2

Answer choices:
1/2cos2m + 1/2cos5m
1/2cos4m - 1/2cos10m
1/2cos10m - 1/2cos4m
1/2cos4m + 1/2cos10m

Answer 3

I think it's either B or D.

Answer 4

\[\large\rm \cos A \cos B=\frac12\left[\cos(A+B)+\cos(A-B)\right]\]
Just plug the stuff into the formula :O

Answer 5

So ya it's uhhh... one of these 4 options +_+

Answer 6

I don't fully understand. Can somebody help?

Answer 7

Your question is

cos(7m)cos(4m)

Use the formula Zepdrix gave you :)

You plug in 7m for A and 4m for B and them simplify, and finally distribute the 1/2 (: