Given: A circle of diameter 40 cm ⇒ radius = 20cm
The length of a chord is 20 cm.
Here, we can see that, the figure forms a equilateral triangle with side length 20 cm
(both radii = 20cm and length of chord = 20cm)
∴ ∠AOB = 60° (∵ Angles in an equilateral triangle are 60° each)
⇒ 60° = 60 × = radians
That is, The Chord AB makes radians at the centre of the circle.
Now, We know that θ = (here, θ is angle subtended by arc)
⇒ l =
∴ Length of the arc AB is cm.
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