7.1  Derivation of formulae

In the diagram, OA and OB are radii and the tangent at A meets OB produced at D. If OA = 1 = OB & q is measured in radians, then OC = cos q AC = sin q AD = tan q arc AB = q

Hence, cos q » 1 & sin q » q » tan q.
 
 
 
 

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