Improper Integral Example

Jason76

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\(\displaystyle \int_{1}^{2} \dfrac{dx}{\sqrt{x -1}}\)

Discontinuity at \(\displaystyle x = 1\)

improper-integral-graph.jpg

\(\displaystyle \int_{b}^{2} \dfrac{dx}{\sqrt{x -1}} dx\)

\(\displaystyle \int_{b}^{2} (x - 1)^{-1/2} dx\)

\(\displaystyle \rightarrow \dfrac{(x - 1)^{1/2}}{\dfrac{1}{2}}\) - evaluated at \(\displaystyle b\) (lower bound) and \(\displaystyle 2\) (upper bound)

\(\displaystyle \rightarrow (2)(x - 1)^{1/2}\) - evaluated at \(\displaystyle b\) (lower bound) and \(\displaystyle 2\) (upper bound)

Now upperbound \(\displaystyle -\) lower bound to find the definite integral.

\(\displaystyle [(2)((2) - 1)^{1/2}] - [(2)((b) - 1)^{1/2}] \)

\(\displaystyle [(2)(1)^{1/2}] - [(2)((b) - 1)^{1/2}] \)

\(\displaystyle [2] - [(2)((b) - 1)^{1/2}] \)

\(\displaystyle \lim b \rightarrow 1^{+}[[2] - [(2)((b) - 1)^{1/2}]] \)

\(\displaystyle \lim b \rightarrow 1^{+}[[2] - [(2)((1) - 1)^{1/2}]] = 2 \) - Because it has a limit, it converges. It's area can be taken, unlike if it diverged. :confused: Is this right. Any error?
 
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\(\displaystyle \int_{1}^{2} \dfrac{dx}{\sqrt{x -1}}\)

Discontinuity at \(\displaystyle x = 1\)

View attachment 3661

\(\displaystyle \int_{b}^{2} \dfrac{dx}{\sqrt{x -1}} dx\)

\(\displaystyle \int_{b}^{2} (x - 1)^{-1/2} dx\)

\(\displaystyle \rightarrow \dfrac{(x - 1)^{1/2}}{\dfrac{1}{2}}\) - evaluated at \(\displaystyle b\) (lower bound) and \(\displaystyle 2\) (upper bound)

\(\displaystyle \rightarrow (2)(x - 1)^{1/2}\) - evaluated at \(\displaystyle b\) (lower bound) and \(\displaystyle 2\) (upper bound)

Now upperbound \(\displaystyle -\) lower bound to find the definite integral.

\(\displaystyle [(2)((2) - 1)^{1/2}] - [(2)((b) - 1)^{1/2}] \)

\(\displaystyle [(2)(1)^{1/2}] - [(2)((b) - 1)^{1/2}] \)

\(\displaystyle [2] - [(2)((b) - 1)^{1/2}] \)

\(\displaystyle \lim b \rightarrow 1^{+}[[2] - [(2)((b) - 1)^{1/2}]] \)

\(\displaystyle \lim b \rightarrow 1^{+}[[2] - [(2)((1) - 1)^{1/2}]] = 2 \) :confused: Is this right. Any error?

I don't see any problem - other than care-less omissons.
 
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