Use the radius of the circle, $\displaystyle\frac{{40}}{{2}}={20}\usepackage{cmbright}\Huge\$ , to find the area of the circle:

$\displaystyle{A}=\pi{{r}}^{{2}}=\pi{{\left({20}\right)}}^{{2}}=\pi\cdot{400}\approx{3.14}\cdot{400}={1},{256}\usepackage{cmbright}\Huge\$ square meters.

The area of the triangle is: $\displaystyle{A}=\frac{{1}}{{2}}{b}\cdot{h}=\frac{{1}}{{2}}\cdot{90}\cdot{90}=\frac{{1}}{{2}}\cdot{8},{100}={4},{050}\usepackage{cmbright}\Huge\$

The area of the shaded region equals the area of the triangle minus the area of the circle. This is approximately $\displaystyle{4},{050}-{1},{256}={2},{794}\usepackage{cmbright}\Huge\$ square meters.