Dear Aspirant,

Kindly know all the formulas for trigonometry,

We know that,

sin A + sin B = 2*[sin(A+B)/2 * cos(A-B)/2]

& Similarly,

cos A - cos B = -2*[sin(A+B)/2 * sin(A-B)/2]

So using these formulas,

= (sin3x + sinx) * sinx + (cos3x - cosx) * cosx

= (2sin2xcosx) * sinx - (2sin2xsinx) * cosx

After multiplying the terms, you'll get 0 as the final result.

Thanks for visiting this site, hope it helped you.