Question 300350
The width (W), length (L), and diagonal (D) form a right triangle which follows the Pythagorean theorem.
{{{W^2+L^2=D^2}}}
{{{L^2=D^2-W^2}}}
{{{L=sqrt(D^2-W^2)}}}
From that, then the area of a rectangle is
{{{A=L*W}}}
{{{highlight_green(A=W*sqrt(D^2-W^2))}}}