Not sure why such an old question is showing up on my feed...
Anyway, let

and

. Then we want to find the exact value of

.
Use the angle difference identity:

and right away we find

. By the Pythagorean theorem, we also find

. (Actually, this could potentially be negative, but let's assume all angles are in the first quadrant for convenience.)
Meanwhile, if

, then (by Pythagorean theorem)

, so

. And from this,

.
So,
Answer:
see below
Step-by-step explanation:
80 = 4* 20
2*2 2 * 10
2 *5
We are breaking the numbers into primes
2*2*2*2*5
(x+2)^5
n = 3
r = 5
3rd term is 5x^3y^2