1.

Evaluate \(\int\limits_{0}^{1}\cfrac{1}{\text x^2+1}d\text x\)

Answer»

Let I = \(\int\limits_{0}^{1}\cfrac{1}{\text x^2+1}d\text x\)

Substituting x=tanθ ⇒ dx=sec2θdθ (By differentiating both sides)

Also, when x=0, θ=0 and x=1 θ = \(\cfrac{\pi}4\)

Since sec2θ=1 + tan2θ

We get I = \(\int\limits_{0}^{\pi/4}d\theta\)

\(\cfrac{\pi}4\)



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