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Question
Find the magnitude of angle A, if 2 tan 3A cos 3A - tan 3A + 1 = 2 cos 3A
Solution
2tan 3A cos 3A – tan 3A + 1 = 2 cos 3A
2 tan 3A cos 3A – tan 3A = 2 cos 3A – 1
tan 3A (2 cos 3A – 1) = 2 cos 3A – 1
(2 cos 3A – 1)(tan 3A – 1) = 0
2 cos 3A – 1 = 0 and tan 3A – 1 = 0
cos 3A = `(1)/(2)` and tan 3A = 1
3A = 60° and 3A = 45°
A = 20° and A = 15°
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