Math

QuestionFind the integral of tan1x1+1x2\frac{\tan^{-1} x}{1 + \frac{1}{x^2}} with respect to xx.

Studdy Solution

STEP 1

Assumptions1. The integral is a definite integral. . The integral is of the form f(x)f(x)dx\int \frac{f'(x)}{f(x)} dx, which can be solved using the logarithmic rule of integration.
3. The function f(x)f(x) is 1+1x1+\frac{1}{x^{}} and its derivative f(x)f'(x) is tan1x\tan ^{-1} x.

STEP 2

First, we need to check if the derivative of the function f(x)f(x) is indeed tan1x\tan ^{-1} x. We can do this by differentiating f(x)f(x).
f(x)=ddx(1+1x2)f'(x) = \frac{d}{dx} \left(1+\frac{1}{x^{2}}\right)

STEP 3

Now, differentiate the function f(x)f(x).
f(x)=02x3f'(x) =0 - \frac{2}{x^3}

STEP 4

We see that the derivative of f(x)f(x) is not tan1x\tan ^{-1} x. Therefore, our initial assumption was incorrect. We need to find a new function f(x)f(x) and its derivative f(x)f'(x) that fit the form of the integral.

STEP 5

Let's rewrite the integral in a more convenient form. Notice that tan1x\tan ^{-1} x is the derivative of 1+1x21+\frac{1}{x^{2}}.
tan1x1+1x2dx=d(1+1x2)1+1x2\int \frac{\tan ^{-1} x}{1+\frac{1}{x^{2}}} dx = \int \frac{d(1+\frac{1}{x^{2}})}{1+\frac{1}{x^{2}}}

STEP 6

Now, we can use the logarithmic rule of integration, which states that f(x)f(x)dx=lnf(x)+C\int \frac{f'(x)}{f(x)} dx = \ln |f(x)| + C.
d(1+1x2)1+1x2=ln1+1x2+C\int \frac{d(1+\frac{1}{x^{2}})}{1+\frac{1}{x^{2}}} = \ln |1+\frac{1}{x^{2}}| + C

STEP 7

The absolute value is unnecessary in this case because 1+1x21+\frac{1}{x^{2}} is always positive. Therefore, the integral simplifies totan1x1+1x2dx=ln(1+1x2)+C\int \frac{\tan ^{-1} x}{1+\frac{1}{x^{2}}} dx = \ln (1+\frac{1}{x^{2}}) + CSo, the solution to the integral tan1x1+1x2dx\int \frac{\tan ^{-1} x}{1+\frac{1}{x^{2}}} dx is ln(1+1x2)+C\ln (1+\frac{1}{x^{2}}) + C.

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