View Single Post
  #4   Spotlight this post!  
Unread 13-03-2005, 21:04
Manoel's Avatar
Manoel Manoel is offline
Registered User
FRC #0383 (Brazilian Machine)
Team Role: Mentor
 
Join Date: Jun 2001
Rookie Year: 2000
Location: Porto Alegre, RS, Brazil
Posts: 608
Manoel has a reputation beyond reputeManoel has a reputation beyond reputeManoel has a reputation beyond reputeManoel has a reputation beyond reputeManoel has a reputation beyond reputeManoel has a reputation beyond reputeManoel has a reputation beyond reputeManoel has a reputation beyond reputeManoel has a reputation beyond reputeManoel has a reputation beyond reputeManoel has a reputation beyond repute
Send a message via ICQ to Manoel Send a message via MSN to Manoel
Re: Proving smallest surface area of cylinder is when h=2r

Sanddrag,

You don't need any volume information at all. Use your second formula and take the partial derivative of A in respect to r, set it to zero and you'll achieve the desired result (except for a nasty negative sign - maybe it's irrelevant, maybe I did something wrong! ). To prove it's a minimum point, take the second partial derivative - you get a positive constant, thus, it is indeed a minimum point.
__________________
Manoel Flores da Cunha
Mentor
Brazilian Machine
Team # 383
Reply With Quote