The shaded sector of the circle below has an area of 4 pi what is the radius of the circle
Hi, So we know that there are 360 degrees in a cirle. 40 degrees of the circle has an area of 4pi. We know that 40/360=1/9th of the total circle so we multiply so 1/9 of the are of the circle equals 40pi
1/9(area of the circle)=4pi
do some algebra and get that the full circle's area is 36pi units^2.
The equation for the are of a circle is pir^2
pir^2=36pi
divide both sides by pi
r^2=36
so this could be -6 or 6 but by convention we know that that a radius can be nagative so my answer is 6
