Using the formula, sin A = √ {1−cos 2A/2} , find the value of sin 30° , it being given that cos 60° = 1/2 .

Question

Using the formula, sin A = \(\sqrt\frac{1-cos2A}2\),find the value of sin 30° , it being given that cos 60° = 1/2.

Answer 1

A = 30°

⇒ 2A = 2 × 30° = 60°

By substituting the value of the given T-ratio, we get:

sin A = \(\sqrt\frac{1-cos2A}2\)

sin 30° = \(\sqrt\frac{1-cos60°}2\)

∴ sin 30° = 1/2