In a circle of diameter 40 cm, the length of a chord is 20 cm. Find the length of minor arc of the chord.
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Solution
Diameter of the circle =40 cm ∴ Radius (r) of the circle =402=20 cm Let AB be a chord (length = 20 cm) of the circle. In △OAB, OA = OB = Radius of circle = 20 cm Also, AB = 20 cm Thus, △OAB is an equilateral triangle. ∴θ=60∘=π3 radian We
know that in a circle of radius r unit, if an arc of length I unit
subtends an angle θ radian at the centre, then
θ=lr ∴π3=arcAB20⟹arcAB=203π cm