Problem involving Power-Reducing Formula

  • #1

Homework Statement


25zi9mr.png



Homework Equations


How in the world did they get their solution? Where did 27/8 come from?


The Attempt at a Solution


I did the arithmetic with the fractions inside before distributing the 9, and ended up getting something like -9/4 cos2x + 9/4 cos4x. Completely different from theirs.
 

Answers and Replies

  • #2
867
0
In the step above that, you have 1/4 + 1/8 = 2/8 + 1/8 = 3/8, then times 9 is 27/8
 

Related Threads on Problem involving Power-Reducing Formula

Replies
1
Views
9K
Replies
4
Views
2K
Replies
9
Views
4K
Replies
4
Views
1K
Replies
7
Views
1K
Replies
16
Views
27K
  • Last Post
Replies
3
Views
1K
Replies
7
Views
2K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
12
Views
2K
Top