How Do You Integrate 4cos(n pi t)?

[Jonny3688]

Homework Statement

integrate:
4*cos(n pi t) d(t)

Homework Equations

The Attempt at a Solution

is it: [4sin(n pi t)]/n.pi

or

[4t sin (n pi t)]/n.pi

any help very much welcome.

 

[HallsofIvy]

What do you get if you differentiate those?

[itex]\int cos(u)du= sin(u)+ C[/edit]. What should you let u be? What is du?

 

[Jonny3688]

What do you get if you differentiate those?

[itex]\int cos(u)du= sin(u)+ C

. What should you let u be? What is du?[/QUOTE]

Thanks for your quick reply, but you have lost me

 

[Jonny3688]

would u = 4

therefore du=0

 

[Mark44]

Nope. Try a different u.

 

[rickz02]

Look at your given and the general solution:

$$\int 4cos(n\pi t) dt$$

$$\int cos(u)du = sin(u)+ C$$

Notice the similarity.