Sunday, August 3, 2014

Indicate one method to solve the integral of y=sin4x*cos6x?

The first step in evaluating the indefinite integral is to
transform the given product of trigonometric functions into a
sum.


We'll apply the
identity:


sin a * cos b =
[sin(a+b)+sin(a-b)]/2


We'll substitute a by 4x and b by
6x.


sin4x*cos6x =
[sin(4x+6x)+sin(4x-6x)]/2


sin4x*cos6x = (sin 10x)/2 - (sin
2x)/2


Now, we'll evaluate the
integral:


Int sin4x*cos6x dx = Int (sin 10x)dx/2 - Int (sin
2x)dx/2


Int (sin 10x)dx = -(cos 10x)/10 +
C


Int (sin2x)dx = -(cos 2x)/2 +
C


The indefinite integral of the given
trigonometric product is: Int sin4x*cos6x dx = -(cos 10x)/20 + (cos 2x)/4 +
C

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