Tuesday, March 17, 2015

How to solve integral of y=x*ln x?

For solving the integral, we'll apply integration by
parts:


Int f(x)dx = Int x*ln
xdx


We'll apply the formula of integration by
parts:


Int udv = uv - Int
vdu


u = ln x


We'll
differentiate both sides:


du =
dx/x


dv = xdx => Int xdx = Int dv =
v


v = x^2/2


We'll substitute
u,v,du,dv in the formula above:


Int x*ln xdx = [(x^2)*(ln
x)]/2 - Int x^2dx/2x


We'll simplify and we'll
get:


Int x*ln xdx = [(x^2)*(ln x)]/2 - x^2/4 +
C


We'll factorize by
x^2/2:


Int x*ln xdx = (x^2/2)*(ln x - 1/2) +
C

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