# Thread: integral by time, can you help me?

1. ## integral by time, can you help me?

hi ,

i want to integrate this, by time:

$\displaystyle \int\dot{y}^2dt$

how can this integrate short?

and can you say me some links about partial differential equations(like hamilton-jacobi in physic, non-linear etc..) i think some text books, or online tutorials, by that themes, and theme "integrate,derive by time."

thanks for you help,

2. $\displaystyle \int y'y' dt = \int y'y'+yy'-yy' dt = \int y'(y+1) dt - \int yy'dt$

In $\displaystyle \int y'(y+1) dt$ let $\displaystyle u=y+1$
In $\displaystyle \int yy'dt$ let $\displaystyle u=y$.

3. i dont understand the following step (maybe its false?),

Originally Posted by ThePerfectHacker
$\displaystyle \int y'y'+yy'-yy' dt = \int y'(y+1) dt - \int yy'dt$
could you write it a bit detailed?