PA and PB are the tangents drawn to a circle with centre O. If PA= 6 cm and APB=`60^0`, then find the length of the chord AB.
Given,
PA = PB (Tangent segments drawn to a circle from an external point are equal)
and ∠APB = `60^0`
∴ In △APB, 
∠PAB = ∠PBA
In △APB, sum of three angles is 180°.
Therefore, ∠PAB + ∠PBA + ∠APB = 180°
= ∠PAB + ∠PBA = 180° - ∠APB
= ∠PAB + ∠PBA = 180° – 60° = 120°
∴ ∠PAB = ∠PBA = 60° (∵ ∠PAB = ∠PBA)
∵ △APB is an equilateral triangle. So, AB = 6 cm