



 
Prem, The length of an arc of a circle is given by
where r is the radius of the circle and θ is the central angle measured in radians. Suppose the length of the chord is c units. In the diagram below R is the midpoint of the chord. sin(θ/2) = QR/PQ = c/(2r) and hence θ = 2 sin^{1}(c/(2r)). Thus
Harley  


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