Vikas TU
Last Activity: 7 Years ago
We know that sin(A+B) = sinAcosB + cosAsinB -----------------1
We know that sin(A - B) = sinAcosB - cosAsinB -----------------2
Now adding 1 and 2
2sinAcosB = sin(A+B) + sin(A - B), so that
sinAcosB = (1/2)[sin(A+B) + sin(A-B)]
let A = 3x and B = 5x
Rewriting the question
(1/2) ∫ [sin8x + sin(-2x)] dx =
(1/2) ∫ [sin8x - sin2x] dx =
=> -1/16 cos8x + 1/4 cos2x + C