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Mathematics 13 Online
OpenStudy (mony01):

Anyone know how to do this?

OpenStudy (mony01):

\[\int\limits_{?}^{?}\frac{ \sin \sqrt{x} }{ \sqrt{x} }\]

OpenStudy (anonymous):

Why does it have question marks on top and bottom of the integral...

OpenStudy (mony01):

oh im not sure theres no numbers in the integral it is just suppose to be the integral by itself

OpenStudy (mony01):

\[\int\limits \frac{ \sin \sqrt{x} }{ \sqrt{x} }\]

OpenStudy (loser66):

let u = \(\sqrt x\)

OpenStudy (mony01):

du=1/2x^-1/2 but how would I substitute this into the integral?

OpenStudy (anonymous):

\[\mathrm d u=\frac{1}{2}x^{-\frac{1}{2}}\mathrm d x=\frac{1}{2\sqrt{x}}\mathrm d x\]

OpenStudy (loser66):

just substitute , \(\int -1/2 sin u du\)

OpenStudy (anonymous):

you can pull the 1/2 (constant) out in front of the integral

OpenStudy (anonymous):

As for the lack of upper and lower limits of integration, it just means you need a general antiderivative (we aren't sure of the constants), so the typical convention is to add +C after you integrate

OpenStudy (anonymous):

where C is any constant

OpenStudy (mony01):

would the answer be \[-\cos \sqrt{x}+C\]

OpenStudy (anonymous):

\[\frac{-1}{2}\int\limits \sin{u}\mathrm d u\] I believe you forgot about the -1/2

OpenStudy (anonymous):

er was it positive 1/2

OpenStudy (anonymous):

Yeah it's positive; my mistake. Otherwise it's correct, so you should have\[-\frac{1}{2}\cos{\sqrt{x}}+C\]

OpenStudy (anonymous):

wait, i may have made another mistake -_-

OpenStudy (anonymous):

found it.\[\mathrm d u=\frac{1}{2\sqrt{x}}\mathrm d x\] \[2\mathrm d u=\frac{1}{\sqrt{x}}\mathrm d x\] Sorry, sloppy maths from me tonight ;) It's a 2 we took in front, not a half.

OpenStudy (mony01):

so its \[2\cos \sqrt{x}+C\]

OpenStudy (anonymous):

\[-2\cos{\sqrt{x}}+C\] since the antiderivative of sin(u) is -cos(u)

OpenStudy (mony01):

thank you so much!!! it was correct!!!

OpenStudy (anonymous):

My pleasure. Sorry about all the mistakes, hope I didn't confuse you ;)

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