Mathematics
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OpenStudy (anonymous):
If I wanted to take the integral of 4/x^2-3, would it be 4ln(x^2-3) divided by the derivative of x^2-3 ?
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OpenStudy (badhi):
try differentiating your assumed answer and see whether you get the expression that needs to be integrated
OpenStudy (anonymous):
no this is an arctan
OpenStudy (anonymous):
So a trig substitution
OpenStudy (anonymous):
-4root(3)/3arctan(root3/3)+c
OpenStudy (anonymous):
x inside the arctan
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OpenStudy (anonymous):
Wouldnt deriv of arctan be \[1/(x^2+1)\]
OpenStudy (anonymous):
\[-\frac{ 4\sqrt{3} }{ 3 }\arctan(\frac{ \sqrt{2} }{ 3 }x)\]
OpenStudy (anonymous):
yes
OpenStudy (anonymous):
i proved that using implicit differentiation, or you may use pyth and trig triangle
OpenStudy (anonymous):
let me give you the link ...
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OpenStudy (anonymous):
i proved the derivative so you can see the integral ...
OpenStudy (anonymous):
integral of the above can be done by substituting x=sqrt(3)*sec u
OpenStudy (anonymous):
alternately u can factorise the denominator and apply partial fraction
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OpenStudy (anonymous):
no its arctanh
OpenStudy (anonymous):
its a parabola trig
OpenStudy (anonymous):
I got it. I would have to use Partial fractions
OpenStudy (anonymous):
yes
OpenStudy (anonymous):
but you can use the identity of tanh and just substitute
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OpenStudy (anonymous):
the required integral is 2/sqrt(3) ln ((x-sqrt(3))/(x+sqrt(3)))+c
OpenStudy (anonymous):
i say its a tanh
OpenStudy (anonymous):
\[\int\limits \frac{ 4 }{ x^2-3}dx\]
OpenStudy (anonymous):
this gives arctanh