If A is an acute angle and tanA + cotA = 2, find the value of 7tan8A - 6cot8A + 8sec2A.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 17.
tanA + cotA = 2
⇒ tanA + 1/tanA = 2
⇒ tan2A + 1 = 2tanA [Multiplying both sides by tanA]
⇒ tan2A - 2tanA + 1 = 0
⇒ (tanA - 1)2 = 0
⇒ tanA = 1 = tan 45°
⇒ A = 45°
Now, 7tan8A - 6cot8A + 8sec2A = 7tan845° - 6cot845° + 8sec245°
= 7(1)8 - 6(1)8 + 8(√2)2
= 7 - 6 + 16
= 17
Therefore, the required value is 17.