Answer:
Explanation:
if you know that the perimeter is 20,
then you have to divide by 4 to get the length of one side
20/4=5.
Draw the diagonal and write in it's length as x.
Use Pythagorean formula
Then know that a2+b2=c2
and use the two side lengths as a and b.
This gives you the equation
5^2+5^2=x^2.
Do the calculations and solve the equation.
25+25=x^2
50=x^2
√50=x.
Therefore x=√50 where x equals the length of the diagonal.