How do you find the antiderivative of cos4(2x)sin3(2x)?

1 Answer
Oct 17, 2017

cos4(2x)sin3(2x)dx=cos7(2x)14cos5(2x)10+C

Explanation:

We have the integral I1=cos4(2x)sin3(2x)dx

Here, let

(2x)=t

ddx(2x)=ddxt

2=dtdx

Therefore, dx=dt2

Put this in I1

I2=12cos4(t)sin3(t)dt

I2=12cos4(t)sin2(t)sin(t)dt

We know (sin2t=1cos2t)

Put this in I2

I2=12cos4(t)(1cos2t)sin(t)dt

Here, let

cost=v

ddtcost=ddtv

sint=dvdt

Therefore,

sin(t)dt=dv

Put this in I2

I3=12v4(1v2)dv

I3=12(v4v6)dv

I3=(12)v55(12)v77+C

Now put in the value of v.

I3=(12)cos5(t)5(12)cos7(t)7+C

Now put in the value of t.

I3=cos5(2x)10+cos7(2x)14+C

Therefore,

cos4(2x)sin3(2x)dx=cos7(2x)14cos5(2x)10+C