sentences:  Let two radii "OA" and "OB" make an arc of θ radians.Since we are considering the limit as "θ" tends to zero, we may assume "θ" is a small positive number, say 0 < θ < ½ π in the first quadrant.In the diagram, let "R"1 be the triangle "OAB", "R"2 the circular sector "OAB", and "R"3 the triangle "OAC".