Help: Calc step

[RobDowneyJr]

I was just looking in the solutions manual for my calc class and I noticed it uses the integration of cos(2x)= sin(x)cos(x). Can someone show how this is true

 

[RobDowneyJr]

n'ermind int(cos(2x)) = 1/2 sin (2x)
and using sin(2x) identity: sin(2x)=2sinxcosx

 

[SOSTrooper]

I predict you'll hit 100 posts by tonight. 😛

I dunno calc.