1. ## finding radius of circle

hello,

calculate the radius of a circle in which the perimeter of a sector of angle 0.5 radians is 20 cm.

can someone please explain how a question of this sort is solved.

i know the length of the arc = $\displaystyle r \theta$ but that is just a part of the perimeter. how do i form an expression for the other side which encloses the arc.

2. The perimeter of a sector would be (length of arc) + 2*(length of radius)

therefore, $\displaystyle 20=2r+r\theta$

3. Originally Posted by nahduma
The perimeter of a sector would be (length of arc) + 2*(length of radius)

therefore, $\displaystyle 20=2r+r\theta$

ohh man, i never realized that the question was so simple. this was one of the last questions so i though it was hard and even though i read that it was the perimeter of the sector, for some strange reason i mixed it up and had it to be the perimeter of the cord, bad judgement on my part. thanks alot for clearing it up though... i would slap myself for that.