We can write above integral as

[Adding and subtracting 1 in denominator]

∵ sin²x + cos²x = 1 and

sin2x = 2 sinx cosx

∵ sin²x + cos²x - 2 sinx cosx = (sinx – cosx)²

Put sinx – cosx = t

Differentiating w.r.t x we get,

(cosx + sinx)dx = dt

Putting values we get,

Putting value of t we get,