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Let I =

Here, we express the denominator in terms (sin x – cos x) which is the integration of numerator.

Clearly,

Therefore, becomes,

Let, sin x – cos x = t.

Then, d(sin x – cos x) = dt

(cos x + sin x)dx = dt.

Now the limits of integration also change,

at x = 0

t = sin0 – cos0 = – 1 and
at x =

∴

OR

(let)

When ; a = 1, b = 3

By, the definition we know that,

As ∴