We will determine the area as follows:
[tex]A=\frac{3}{4}\pi r^2\Rightarrow A=\frac{3}{4}(3.14)(3)^2[/tex][tex]\Rightarrow A=21.195\Rightarrow A\approx21.2[/tex]
So, the area of the sector is approximately 21.2 square units.
(The reason it is multiplied by 3/4 is that the normal area of a circumference is given by pir^2 [Whole circle], but since it is stated that the missing area has an angle of 90°, then the remainder of the circle [Area to find] is 3/4 of the original are).
