Question

If sin (a) +cos (a) =1.2, then what is sin(a)^3 + cos(a)^3?
I was having some trouble with this problem. I got .98 as an estimate. Why is this wrong!!!1

Answer 1

Why not show how you arrived at that value?

If (sin+cos)=1.2,
(sin+cos)^2 = 1.44
sin^2+2sin*cos+cos^2 = 1.44
1+2sin*cos = 1.44
sin*cos = .22

since (x+y)^3 = (x+y)(x^2-xy+y^2)

(sin^3+cos^3) = (sin+cos)(sin^2-sin*cos+cos^2)
= (sin+cos)(1-sin*cos)
= 1.2 * 0.78
= 0.936

Answer 2

Thanks! Actually, I had like the same method as you for like the first few steps then I had a miscalculation