Q43 / 104 · NTA Abhyas (JEE Main) 2020 · Mathematics · Indefinite Integration

The integral Ι=∫sinx2+2x2cosx2dx=xHx+C, (where C is the constant of integration). If the range of H(x) is a,b, then the value of  a+2b is equal to

Correct answer: 1

Solution

Given integral Ι=∫1⋅sinx2+x⋅2xcosx2dx
∵∫f'g+f⋅g'dx=∫fg'dx=f⋅g+C
=x⋅sinx2+C
∴ Hx=sinx2, whose range is -1,1
∴ a=-1, b=1⇒a+2b=1

Hence, the correct answer is 1.

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