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Question : If (sin $\alpha$ + cosec $\alpha$)+ (cos $\alpha$ + sec $\alpha$)= k + tan$\alpha$ + cot$\alpha$, then the value of k is:

Option 1: 1

Option 2: 7

Option 3: 3

Option 4: 5


Team Careers360 18th Jan, 2024
Answer (1)
Team Careers360 25th Jan, 2024

Correct Answer: 7


Solution : (sin $\alpha$ + cosec $\alpha$) 2 + (cos $\alpha$ + sec $\alpha$) 2 = k + tan 2 $\alpha$ + cot 2 $\alpha$
Taking the left-hand side of the expression, we get,
(sin $\alpha$ + cosec $\alpha$) 2 + (cos $\alpha$ + sec $\alpha$) 2
= sin 2 $\alpha$ + cosec 2 $\alpha$ + 2sin $\alpha$cosec $\alpha$ + cos 2 $\alpha$ + sec 2 $\alpha$ + 2cos $\alpha$sec $\alpha$
= (sin 2 $\alpha$ + cos 2 $\alpha$) + cosec 2 $\alpha$ + 2 + sec 2 $\alpha$ + 2
We know that sin 2 $\alpha$ + cos 2 $\alpha$ = 1.
= 5 + cosec 2 $\alpha$ + sec 2 $\alpha$
= 5 + (1 + cot 2 $\alpha$) + (1 + tan 2 $\alpha$)
= 7 + tan 2 $\alpha$ + cot 2 $\alpha$
Comparing it with the right-hand side, we get, k = 7
Hence, the correct answer is 7.

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