Question:

Integrate the function: \(\frac {x-1}{\sqrt {x^2-1}}\)

Updated On: Oct 4, 2023
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Solution and Explanation

\(∫\frac {x-1}{\sqrt {x^2-1}}\  dx\) = \(∫\frac {x}{\sqrt {x^2-1}}\  dx\) - \(∫\frac {1}{\sqrt {x^2-1}}\  dx\)            ……....(1)

\(For ∫\frac {x}{\sqrt {x^2-1}} dx, \ let x^2-1 = t ⇒ 2x dx = dt\)

\(∴ ∫\frac {x}{\sqrt {x^2-1}} dx = \frac 12 ∫\frac {dt}{\sqrt t}\)

\(=\frac 12 ∫t^{-\frac 12} dt\)

\(=\frac 12[2t^{\frac 12}]\)

\(=\sqrt t\)

\(=\sqrt {x^2-1}\)

\(From\  (1), we\  obtain\)

\(∫\frac {x-1}{\sqrt {x^2-1}}\  dx\) = \(∫\frac {x}{\sqrt {x^2-1}}\  dx\) - \(∫\frac {1}{\sqrt {x^2-1}}\  dx\)         \([∫\frac {1}{\sqrt {x^2-a^2}} \ dt = log\ |x+\sqrt {x^2-a^2|}]\)

\(= \sqrt {x^2-1}-log|x+\sqrt {x^2-1}|+C\)

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Concepts Used:

Integrals of Some Particular Functions

There are many important integration formulas which are applied to integrate many other standard integrals. In this article, we will take a look at the integrals of these particular functions and see how they are used in several other standard integrals.

Integrals of Some Particular Functions:

  • ∫1/(x2 – a2) dx = (1/2a) log|(x – a)/(x + a)| + C
  • ∫1/(a2 – x2) dx = (1/2a) log|(a + x)/(a – x)| + C
  • ∫1/(x2 + a2) dx = (1/a) tan-1(x/a) + C
  • ∫1/√(x2 – a2) dx = log|x + √(x2 – a2)| + C
  • ∫1/√(a2 – x2) dx = sin-1(x/a) + C
  • ∫1/√(x2 + a2) dx = log|x + √(x2 + a2)| + C

These are tabulated below along with the meaning of each part.