Question

If 3 tan2 - 1 = 0, find cos 20, given that is acute.


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Answer 1

Solution :-

Let theta = A

3tan²A - 1 = 0

3tan²A = 1

tan²A = 1/3

tan A = √(1/3)

tan A = 1/√3

tan A = tan 30

A = 30

Now,

Cos 2A = Cos ( 2 × 30) = Cos 60 = 1/2

Cos²A = Cos ² 30 = (√3/2)² = 3/4

Answer 2

Answer:

Hope it helps...........