# Math Help - sector area

1. ## sector area

Chord length c in circle radius r.
What is area of the sector created, in terms of c and r?

2. Originally Posted by Wilmer
Chord length c in circle radius r.
What is area of the sector created, in terms of c and r?
Hi Wilmer,

You can use the Cosine Rule.

The sector angle C is derived from $c^2=R^2+R^2-2RRCosC$

$C=Cos^{-1}\left(\frac{2R^2-c^2}{2R^2}\right)$

Then use this C for the sector area.

3. Thanks (I knew that), BUT without using trig.
In terms of r and c ONLY.