Using the hint given and substituting x + y = z

Differentiating z – x with respect to x

Integrate

We know that cos 2z = 2 cos²z – 1

and sin 2z = 2 sin z cos z

Let hence differentiating with respect to z

we get

hence

⇒ log t + c = x

Resubstituting t

Resubstitute z