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Find tan 9° − tan 27° − tan 63° + tan 81°.
A2
B4
C1
D8
Answer & Solution
Correct answer: B. 4
Pairing tan 81° + tan 9° and tan 63° + tan 27° as cotangent-tangent sums gives 2/sin 18° − 2/sin 54°, which equals 4.
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