Question

Using the formula, `sin A = sqrt((1 - cos 2A)/2)`, find the value of sin 30°, it being given that `cos 60^circ = 1/2`.

Answer 1

A = 30⁰
⇒ 2A = 2 × 300 = 60⁰ 
By substituting the value of the given T-ratio, we get:

sin A =`sqrt((1- cos 2A)/2)`

sin `30^0 = sqrt((1-cos 60^0)/2) = sqrt(1-1/2)/2 = sqrt((1/2)/2) = sqrt(1/4) =1/2`

∴ sin `30^0 = 1/2`