We'll calculate the antiderivative F(x) integrating the
given function.
F(x) is a function such as dF/dx =
f(x).
Int f(x)dx = F(x) +
C
We'll write the function as a
product:
(sinx)^3 = (sinx)^2*sin
x
We'll integrate both
sides:
Int (sinx)^3dx = Int [(sinx)^2*sin
x]dx
We'll write (sinx)^2 = 1 -
(cosx)^2
Int [(sinx)^2*sin x]dx = Int [(1 - (cosx)^2)*sin
x]dx
We'll remove the
brackets:
Int [(1 - (cosx)^2)*sin x]dx = Int sin xdx - Int
(cosx)^2*sin xdx
We'll solve Int (cosx)^2*sin xdx using
substitution technique:
cos x =
t
We'll differentiate both
sides:
cos xdx = dt
We'll
re-write the integral, changing the variable:
Int
(cosx)^2*sin xdx = Int t^2dt
Int t^2dt = t^3/3 +
C
Int (cosx)^2*sin xdx = (cos x)^3/3 +
C
Int (sinx)^3dx = Int sin xdx - Int (cosx)^2*sin
xdx
Int (sinx)^3dx = -cos x - (cos x)^3/3 +
C
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