d/dp sqrt((p/2-a*p)*(p/2-b*p)*(p/2-c*p)*(p/2-p*(1-a-b-c)))

Uh oh! Wolfram|Alpha doesn't run without JavaScript.

Please enable JavaScript. If you don't know how, you can find instructionshere.Once you've done that, refresh this page to start using Wolfram|Alpha.