alleryFind cos(75°) using cos(A + B):
A√3/2
B(√3 - 1)/(2√2)
C1/2
D(√3 + 1)/(2√2)
Answer & Solution
Correct answer: B. (√3 - 1)/(2√2)
We have cos(75°) = cos(45° + 30°).
Then cos(75°) = cos45 cos30 - sin45.
Then sin30 = (1/√2)(√3/2) - (1/√2)(1/2).
So sin30 = (√3 - 1)/(2√2).
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