Using properties of integral, evaluate
OR
Find: 
We know,

Let ![]()
Now,








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⇒ I = π
OR
Dividing numerator and denominator by cos3x

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Put tanx = t, then sec2xdx = dt
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By partial fractions
Let ![]()
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⇒ t = At2 – At + A + Bt + Bt2 + Ct + C
⇒ t = t2(A + B) + (-A + B + C) t + A + C
On comparing, A + B = 0
-A + B + C = 1, A + C = 0
On solving,
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∴

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Where, u = t2 – t + 1 and du = 2t – 1

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Couldn't generate an explanation.
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