Wednesday, January 18, 2017

`f(x) = (2x)/(1 + x^2)^2, [0, 2]` Find the average value of the function on the given interval.

Given `f(x)=(2x)/(1+x^2)^2, [0, 2]`


Average Value Formula=`1/(b-a)int_a^bf(x)dx`



`f_(ave)=1/(2-0)int_0^2(2x)/(1+x^2)^2dx`


`=(1/2)*2int_0^2x/(1+x^2)^2dx`


`=int_0^2x/(1+x^2)^2dx`


Integrate using the u-subsitution method.


Let `u=1+x^2`


`(du)/dx=2x`


`dx=(du)/(2x)`



`=int_0^2x/u^2*(du)/(2x)`


`=(1/2)int_0^2(1/u^2)du`


`=(1/2)int_0^2(u^-2)du`


`=(1/2)(u^-1)/(-1)|_0^2`


`=(-1/2)[1/u]_0^2`


`=(-1/2)[1/(1+x^2)]_0^2`


`=(-1/2)[1/(1+(2)^2)-1/(1-0^2)]`


`=(-1/2)[1/5-1]`


`=(-1/2)(-4/5)`


`=2/5`



The average value is 2/5.


Given `f(x)=(2x)/(1+x^2)^2, [0, 2]`


Average Value Formula=`1/(b-a)int_a^bf(x)dx`



`f_(ave)=1/(2-0)int_0^2(2x)/(1+x^2)^2dx`


`=(1/2)*2int_0^2x/(1+x^2)^2dx`


`=int_0^2x/(1+x^2)^2dx`


Integrate using the u-subsitution method.


Let `u=1+x^2`


`(du)/dx=2x`


`dx=(du)/(2x)`



`=int_0^2x/u^2*(du)/(2x)`


`=(1/2)int_0^2(1/u^2)du`


`=(1/2)int_0^2(u^-2)du`


`=(1/2)(u^-1)/(-1)|_0^2`


`=(-1/2)[1/u]_0^2`


`=(-1/2)[1/(1+x^2)]_0^2`


`=(-1/2)[1/(1+(2)^2)-1/(1-0^2)]`


`=(-1/2)[1/5-1]`


`=(-1/2)(-4/5)`


`=2/5`



The average value is 2/5.


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