Q. \(\displaystyle \int x^{-1}\,dx\)
Answer
We need to find
\[
\int x^{-1}\,dx
\]
Since \(x^{-1}=\frac{1}{x}\), we use the rule \(\int \frac{1}{x}\,dx=\ln|x|+C\).
\[
\int x^{-1}\,dx=\ln|x|+C
\]
Detailed Explanation
We want to compute the integral
\[
\int x^{-1}\,dx
\]
Step 1: Rewrite the power in a more familiar form.
The exponent \( -1 \) means we have the reciprocal of \(x\):
\[
x^{-1}=\frac{1}{x}
\]
So the integral becomes
\[
\int \frac{1}{x}\,dx
\]
Step 2: Use the standard logarithm integral rule.
A key fact from calculus is that
\[
\int \frac{1}{x}\,dx=\ln|x|+C
\]
Step 3: State the final answer.
\[
\int x^{-1}\,dx=\ln|x|+C
\]
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Calculus FAQ
What is \(\\int x^{-1} \\, dx\) ?
\(\displaystyle \\int x^{-1} \\, dx = \\ln|x| + C\).
Why does the answer involve absolute value \( |x| \) ?
\(\ln(x)\) is only defined for \(x>0\). Using \(\\ln|x|\) ensures the derivative is \(1/x\) for both \(x>0\) and \(x<0\), excluding \(x=0\).
What is \(\\int \\frac{1}{x} \\, dx\) ?
\(\displaystyle \\int \\frac{1}{x} \\, dx = \\ln|x| + C\).
What happens if I differentiate the result \(\\ln|x| + C\) ?
\(\displaystyle \\frac{d}{dx}(\\ln|x|)=\\frac{1}{x}\). The constant \(C\) differentiates to \(0\).
Is there a simpler method to integrate \(x^{-1}\) ?
Use the power rule: for \(n\\neq -1\), \(\\int x^n dx=\\frac{x^{n+1}}{n+1}+C\). Since \(n=-1\), it becomes \(\\ln|x|+C\).
What is the definite integral \(\\int_{a}^{b} \\frac{1}{x} \\, dx\) ?
For \(a,b\\neq 0\) and same sign: \(\displaystyle \\int_{a}^{b} \\frac{1}{x} dx = \\ln|b| - \\ln|a| = \\ln\\left|\\frac{b}{a}\\right|\).
Solve the integral of 1/x!
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