# Math Help - Circles

1. ## Circles

Okay, I have a question on an exam paper that I just can't seem to do.

Well okay. It's a circle. It's been cut. So we have a triangle and a sector.

The radius is 4cm. The sector area is Acm^2 and the perimeter is Xcm and X = 3A.

Now. I have to show with that information that the angle is 0.4radians.

I can't figure it out.

I need to figure out the perimeter. Then I can just sub it into 1/2*R^2*the angle in radians and then BAM I should have showed it.

2. Originally Posted by StephenPoco
Okay, I have a question on an exam paper that I just can't seem to do.

Well okay. It's a circle. It's been cut. So we have a triangle and a sector.

The radius is 4cm. The sector area is Acm^2 and the perimeter is Xcm and X = 3A.

Now. I have to show with that information that the angle is 0.4radians.

I can't figure it out.

I need to figure out the perimeter. Then I can just sub it into 1/2*R^2*the angle in radians and then BAM I should have showed it.

clarify your question.When you cut the circle you have a sector which consists of a . triangle and a segment What is A?

3. Silly me. Suddenly all makes sense.

Well you see. I read the question a bit queerly. You see, I thought X was the perimeter of the triangle, but upon reading again I found out X was actually the perimeter of the sector.

So X = rθ +2r = 4θ + 8
A = 0.5r²θ = 8θ
So X = 24θ = 4θ + 8

From then I got that θ = 0.4

I always make these damned silly mistakes.