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Evaluate the integral and express your answer in simplest form.

int(9)/(xsqrt(x^(2)-1))dx
Answer:

Evaluate the integral and express your answer in simplest form.\newline9xx21dx \int \frac{9}{x \sqrt{x^{2}-1}} d x \newlineAnswer:

Full solution

Q. Evaluate the integral and express your answer in simplest form.\newline9xx21dx \int \frac{9}{x \sqrt{x^{2}-1}} d x \newlineAnswer:
  1. Recognize standard inverse trigonometric form: Recognize the integral as a standard inverse trigonometric form. The integral resembles the form of the derivative of inverse hyperbolic functions, specifically the inverse hyperbolic secant. The standard form is 1xx21dx=arcsech(x)+C\int \frac{1}{x\sqrt{x^2-1}}\,dx = \text{arcsech}(x) + C, where CC is the constant of integration.
  2. Factor out constant: Factor out the constant from the integral. The integral can be rewritten by factoring out the constant 99: I=9xx21dx=9×1xx21dxI = \int \frac{9}{x\sqrt{x^2-1}}\,dx = 9 \times \int \frac{1}{x\sqrt{x^2-1}}\,dx
  3. Apply standard form: Apply the standard form of the inverse hyperbolic secant.\newlineUsing the standard form, we can write the integral as:\newlineI=9×arcsech(x)+CI = 9 \times \text{arcsech}(x) + C\newlineHowever, we need to express the answer in terms of the natural logarithm, as the arcsech\text{arcsech} function is not commonly used in simplest form.
  4. Express in natural logarithm: Express arcsech(x)\text{arcsech}(x) in terms of natural logarithm.\newlineThe inverse hyperbolic secant can be expressed as:\newlinearcsech(x)=ln(1x+1x21)\text{arcsech}(x) = \ln(\frac{1}{x} + \sqrt{\frac{1}{x^2} - 1})
  5. Substitute into integral: Substitute the expression for arcsech(x)\text{arcsech}(x) into the integral.I=9ln(1x+1x21)+CI = 9 \cdot \ln\left(\frac{1}{x} + \sqrt{\frac{1}{x^2} - 1}\right) + C
  6. Simplify inside logarithm: Simplify the expression inside the logarithm.\newlineSince we have 1x\frac{1}{x} inside the logarithm, we can simplify the expression by multiplying the numerator and denominator by xx:\newlineI=9ln(1+x21x)+CI = 9 \cdot \ln\left(\frac{1 + \sqrt{x^2 - 1}}{x}\right) + C
  7. Check for errors: Check for any possible simplifications or errors.\newlineThe expression inside the logarithm is already in its simplest form, and there are no apparent math errors.

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