Question 70

Find the value $$sin75^\circ$$?

Solution

sin(A+B) ≡ sin(A)cos(B) + sin(B)cos(A)

⇒ sin(75°) = sin(30+45)° = sin(30°)cos(45°) + sin(45°)cos(30°)

= ½ × 1/√2 + 1/√2 ×(√3)/2 = 1/(2√2) + (√3)/(2√2)

= (1+√3)/(2√2)

=(√2+√6)/4.
B is correct choice.


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