Question

Question #f57ae

Answer 1

There are many ways to prove that sin 60 = sin 120.
1. By unit circle.
On the unit circle, the arc `60^@` and the arc `120^@` have the same sin value `(sqrt3/2)`.
2. By Table of special arcs:
On the Table --> `sin 60 = sin 120 = sqrt3/2`
3. By trig identity:
sin 2a = 2sina.cos a
sin 120 = 2sin 60.cos 60.
Trig table gives `cos 60 = 1/2`, there for sin 120 = sin 60