## Length of the Diagonal of an Isosceles Trapezium

Drao a vertical line from to E and another from B to F.

\[ED=CF=x\]

and \[8 +2x=12\]

since \[AB=EF\]

. Hence \[x=2\]

.Now draw the right angled triangle DBF.

Then

\[DF= \sqrt{DF^2 +FB^2} =\sqrt{10^2+9^2} =13.45 cm\]