# C4 Integration Question - Help!Watch

#1
I'm not too good with integration, but can anyone help me with integrating this?

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10 years ago
#2
I cant see anything?
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10 years ago
#3
Whats the bit after that? the bit your meant to intergrate!?
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#4
sorry - clicked post instead of preview :P
will post the revised version in a minute
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10 years ago
#5
Never have I seen quite so thrilling an integral.
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#6
Here it is -

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10 years ago
#7
Try a substitution x=sin(u).
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10 years ago
#8
you need to use a substitution, x=sinu or cosu will work
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#9
I don't understand how to do it though?
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10 years ago
#10
(Original post by Kittyyyyyyy)
I don't understand how to do it though?
Where have you got up to. Post any ideas/working you have.
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10 years ago
#11
dont you just integrate by recognition

to get x/sqrt(1-x^2)
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10 years ago
#12
(Original post by Creative)
dont you just integrate by recognition

to get x/sqrt(1-x^2)
No - that's not right.
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10 years ago
#13
(Original post by Kittyyyyyyy)
I don't understand how to do it though?
what you do is, replace the x in the integrand with sinu and then for dx. differentiate x = sin u with respect to u, and then make dx the subject and replace dx with whatever your result was.
For the limits, find u when x= 0 and at x=1/2. Then simplify things and the integral should be simple to evaluate from there.
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10 years ago
#14
(Original post by Creative)
dont you just integrate by recognition

to get x/sqrt(1-x^2)
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#15
I don't know how to start it or anything, being incredibly thick at integration.
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10 years ago
#16
Start off using the substitution

x=sinu

and then differentiate that and see what you can replace
so you have

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10 years ago
#17
(Original post by silent ninja)
yeah i get the original integral if I do that

( unless i'm doing something wrong :P ), used product rule to differentiate.
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10 years ago
#18
I'll start you off:

If you substitute x=sinu you get:

Now find to find dx in terms of du and substitute...
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10 years ago
#19
(Original post by Creative)
yeah i get the original integral if I do that

( unless i'm doing something wrong :P ), used product rule to differentiate.

Product or quotient rule, you are doing something wrong

Op, have you done any integration by substitution before?
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#20
Using could I just do the same?
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