Integrating (2/a)[200sin(3πx)sin(nπx/a)] from 0 to a

[maherelharake]

Homework Statement

I need to integrate


(2/a) [200sin(3*Pi*x)sin(n*pi*x/a)] from 0 to a. In this equation , 'a' is a constant. I don't have to show my work, just the final answer.

Homework Equations

The Attempt at a Solution

I used a website, and got a result which I have attached. This online calculator does not plug in the bounds. However, this doesn't seem correct to me. I tried to integrate it by parts (to check), but couldn't get it to work. Any help? Thanks.

 

[Inferior89]

If you only want to find an answer you can use www.wolframalpha.com and tell it:
"integrate f(x) dx from 0 to a"
where f(x) is your function.

However, it is always good to know how to do stuff by hand. I think two integrations by parts should work.

 

[maherelharake]

Ok so what I inputted was this...

integrate (2/a)[200sin(3*Pi*x)sin(n*pi*x/a)dx from 0 to a

I couldn't get it to give me a definite result. It gave me an indefinite result, but I would like to learn how to use this site properly too.

 

[Inferior89]

Because your delimiters are wrong. Don't use "[" especially when you don't have a closing "]".

http://www.wolframalpha.com/input/?i=integrate+(2/a)(200sin(3*Pi*x)sin(n*pi*x/a))++dx+from+0+to+a

 

[maherelharake]

Ohhh ok. Thanks.