Suppose we let
, so that
.
Also, recall the double angle identity for cosine:

So, we can rewrite and compute the integral using the substitution, as





Answer:
x=-4
Step-by-step explanation:
brainliest please
Remember you can do anything to an equation as long as you do it to both sides
x+9=18-2x
add 2x to both sides
2x+x+9=18+2x-2x
3x+9=18+0
3x+9=18
minus 9 both sides
3x+9-9=18-9
3x+0=9
3x=9
divide both sides by 3
(3x)/3=9/3
(3/3)x=3
1x=3
x=3