Question #f57ae

1 Answer
Nghi N.
Feb 17, 2017

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

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