Why the value of sin120 equal to sin60?

1 Answer
Write your answer here...
Start with a one sentence answer
Then teach the underlying concepts
Don't copy without citing sources


Write a one sentence answer...



Explain in detail...


I want someone to double check my answer

Describe your changes (optional) 200

Nghi N. Share
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

Was this helpful? Let the contributor know!
Impact of this question
Answer impact map
282 views around the world
You can reuse this answer
Creative Commons License