If 2 tan x + 3 cot x = 5, then the value of 4tan2x + 9cot2x is:
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Correct answer: D
Explanation
The correct answer is option 4 i.e. 13.
2 tan x + 3 cot x = 5
Squaring of both sides, we get
4 tan²x + 9 cot²x + 2.(2 tan x).(3 cot x) = 25
⇒ 4 tan²x + 9 cot²x + 12 = 25
⇒ 4 tan²x + 9 cot²x = 13