We write the integral as:
Int
(sin x)^n*cos xdx
We notice that the derivative of sin x is
cos x. We'll substitute:
sin x =
t
We'll differentiate both
sides:
cos xdx = dt
We'll
re-write the integral in t:
Int t^n*dt = t^(n+1)/(n+1) +
C
But t = sin x
Int (sin
x)^n*cos xdx = (sin x)^(n+1)/(n+1) + C
We'll determine F(b)
for b = pi/2:
F(pi/2) = (sin
pi/2)^(n+1)/(n+1)
F(pi/2) =
1^(n+1)/(n+1)
F(pi/2) =
1/(n+1)
F(0) = 0, for sin 0 =
0
Int (sin x)^n*cos xdx = F(pi/2) -
F(0)
Int (sin x)^n*cos xdx =
1/(n+1)
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