Find the exact value of sin

Question

Find the exact value of: sin(75?)

Answer 1

Or:

 

sin 75 = sin (45 + 30) and use sum formula.

Answer 2

sin 75 = sin (150/2) = ±√[(1-cos150)/2]= ±√[(1+√3/2)/2]=±√[(2+√3)/4]= ±1/2√(2+√3)

since it is in the first quandrant, we take the positive value1/2√(2+√3) .