Wednesday, October 3, 2012

Using integral calculus integrate the function dy/y^2+8y+20

In other words, we'll have to calculate the indefinite
integral of the given
function:


Int dy/(y^2+8y+20)


We
can re-write the denominator by completing the
square:


(y^2+8y+16) - 16 + 20 = (y+4)^2 + 4 = (y+4)^2 +
2^2


Int dy/(y^2+8y+20) = Int dy/[(y+4)^2 +
2^2]


We'll note y + 4 = t => dy =
dt


Int dy/[(y+4)^2 + 2^2] = Int dt/(t^2 +
2^2)


Int dt/(t^2 + 2^2) = (1/2)*arctan (t/2) +
c


The final result is: Int dy/(y^2+8y+20) =
(1/2)*arctan [(y+4)/2]+ c

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