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Mathematics 25 Online
OpenStudy (anonymous):

S dx/sqrt(3+2x-x^2)

OpenStudy (phi):

when you see sqrt in the denominator perhaps the integral will be an inverse trig function http://www.math.brown.edu/UTRA/trigderivs.html#inverses Try to "complete the square" on -x^2 + 2x

OpenStudy (anonymous):

i got a square of 4-(x-1)^2

OpenStudy (anonymous):

after simplifying the sqrt i got dx/-x+1 which becames -ln|-x+1|+c

OpenStudy (phi):

you mean square root: \[ \int \frac{dx}{\sqrt{4 - (x-1)^2} }\] factor 4 from out of the square root: \[ \int \frac{dx}{2\sqrt{1 - \frac{(x-1)^2}{4}} }\\ \int \frac{dx}{2\sqrt{1 - \left(\frac{x-1}{2}\right)^2} } \]

OpenStudy (phi):

let u = (x-1)/2 find du in terms of dx, solve for dx and sub in what do you get ?

OpenStudy (anonymous):

i split the square root \[\frac{ dx }{\sqrt{4-(x-1)^2} } \to \frac{ dx }{ 2-x-1 }\] is that wrong?

OpenStudy (phi):

unfortunately , the square root of 4 - (x-1)^2 is not what you wrote 2-x-1 (or more simply 1-x ) squared is (1-2x+x^2) on the other hand 4-(x-1)^2 is 4 - x^2 +2x -1 = -x^2+2x+3 so you have to keep the radical sign. But if you use the substitution u = (x-1)/2 you will get an expression that can be integrated using the formula for the inverse sign.

OpenStudy (phi):

***inverse sine

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