Answer:
√(2 + √3)/4
Step-by-step explanation:
Sine 5π/12 = Sine (5π/6)/2
Recall
π = 180°
Thus,
Sine (5π/6)/2 = Sine (5×180 /6)/2
= Sine 150/2
Recall
Sine θ/2 = √(1 – Cos θ)/2
Thus,
Sine 150/2 = √(1 – Cos 150)/2
But, Cosine is negative in the 2nd quadrant. Thus,
Cos 150 = – Cos 30 = –√3/2
Thus,
√(1 – Cos 150)/2 = √(1 – –√3/2 )/2
= √(1 + √3/2 )/2
= √[(2 + √3)/2 ÷ 2]
= √[(2 + √3)/2 × 1/2]
= √(2 + √3)/4
Therefore,
Sine 5π/12 = √(2 + √3)/4
