flipflopchic said:
i have to find the radius. The book says that the shaded area of the cirlc is 12 pi cm squared. The shaded area equals 120degrees. In the back of the book it tells me to set the equation up like this:
1/3 pi r squared = 12 pi.
how do i solve this?
and im sorry im new to this
We can't see your diagram, of course. So, I'm assuming that the "shaded area of the circle" is like a piece of a pie.
The angle at the center of the circle is 120 degrees.
Now, 120 degrees is 120/360 of the whole circle, so the area included in the sector formed by two radii intersecting at the center of the circle, at an angle of 120 degrees, is 120/360, or 1/3 of the area of the circle.
For a circle,
A = pi * r[sup:3blgjou8]2[/sup:3blgjou8]
You know that the area is 12 pi. And, you're looking for the radius.
The area of the sector is (1/3)*Area of circle, or, (1/3)*pi*r[sup:3blgjou8]2[/sup:3blgjou8]
12 pi = (1/3)*pi*r[sup:3blgjou8]2[/sup:3blgjou8]
Can you solve that for r?
