Engineering
Mathematics
Integration by Substitution
Question

Let I(x)=6sin2x(1-cotx)2dx. If I (0) = 3, then Iπ12 is equal to

23  

33 

3 

63 

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Solution

I(x)=6cosec2x(1-cotx)2dx,ddx(1-cotx)=cosec2x 

Put t = 1 – cot x

I(x)=6dtt2=-6sinx(sinx-cosx)+C 

x = 0 ⇒  3 = 0 + C

x=π12Iπ12=-63-1223-122-3+122+3=33