i have a verrrry simple question but i
just cant think of the answer...
how do you find the length of a 
parallelograms diagonal??
i need it quick,,,


Diagonal of a parallelogram = the square root of the 
sum of the squares of two adjacent sides reduced by 
twice their product times the cosine of the angle 
opposite the diagonal desired.

In other words 

  D______________C
  / .          ./
 /      .      / 
/·____________/
A              B

There are two diagonals, AC and BD

               _________________________
diagonal AC = ÖAB² + BC² - 2×AB×BC×cosÐB

               _________________________
diagonal BD = ÖAB² + BC² - 2×AB×BC×cosÐA

Edwin