



 
Hi Benson, Since the triangle that is created by the radii and the chord do not make a right triangle, we have to use the Law of Cosine. In my diagram, the chord length is c and the radii are a & b. Using the law of cosine solve for angle C which is the angle across from side c, this is your sector angle. You can then use the arc length formula Hope this helps, Janice  


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