Q.Integrate the following function:
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Start your 14-day free trial to unlock the full solution →The integral of is solved using integration by parts, treating as the first function and as the second function. The final result is .
Why Integration by Parts?
The function (also written as ) is an inverse trigonometric function. There is no direct formula for its integral — you cannot reverse-differentiate it by inspection. But integration by parts gives us a way: it lets us trade a hard integral for an easier one.
The rule is:
The trick is to choose and so that the new integral is simpler. For , the derivative is a rational function — much easier to integrate than the original inverse trig function. So we set:
- (so )
- (so )
This is the classic choice: the inverse trig function becomes the , and the "1" becomes the .
A common mistake is to set and . That would require integrating directly — which is exactly what we're trying to find! Always let the function whose derivative is simpler be .
Step-by-step solution
- Set up integration by parts We have:
Choose:
Then:
- Apply the formula
Substituting:
So:
- Solve the new integral …
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