Intergal current solution question

[transgalactic]

here is the question and solution:

http://i40.tinypic.com/2jd0xnd.gif

its illegal to write an interval t and variable dt

and i can't see how they get their expression.
i got a different result
$$dq=\int_{0}^{t}Idt'=It-0$$

even if i substitute in I the expression that i was given
i still get a different result
??

 

[Cyosis]

You assumed I was constant. The exercise, however, gives you an I that depends on t. You need to integrate that function. What result do you get when using that expression?

 

[transgalactic]

worked thanks :)