Question

How do you use half angle formula to find sin 15?

Answer 1

`sin^2(theta/2) = 1/2(1-cos(theta))`

`sin^2(15^o) = 1/2(1-cos(30^o))`

`cos(30^o)`
is the cosine of one of the standard triangles and
`cos(30^o) = sqrt(3)/2`

So
`sin(15^o) = 1/2(1-sqrt(3)/2)`

`= (2-sqrt(3))/4`