Given a triangle with base b and perpendicular height h, then
[tex]\text{ the area of the triangle = }\frac{1}{2}\times bh[/tex]b = m, h = n,
[tex]\text{ the area of the triangle = }\frac{1}{2}mn[/tex]Given a rectangle with length l and width w, then
[tex]\text{ the area of the rectangle = }l\times w[/tex]In this case,
l = n and w = m
Therefore,
[tex]\text{ the area of the rectangle = }mn[/tex]Therefore,
the area of the triangle TRI is half the area of the rectangle RECT
