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Prove that Cos 5A + cos 7A/ sin 5A+ sin 7A = cot 6A ?

Prove that Cos 5A + cos 7A/ sin 5A+ sin 7A = cot 6A ?

Grade:11

2 Answers

Arun
25750 Points
6 years ago
we have to put the formulas of cosC+ cosD & sinC+sinD
Now
(2 cos6A cosA)/(2 sin6A cosA)
cos6A/sin6A
cot6A
Hence Proved
Vikas TU
14149 Points
6 years ago
Dear Student,
Writing it to other form as:
(cos5a+cos7a)/(sin5a+sin7a)=2cos(((5a+7a))⁄2)cos(((5a-7a))⁄2)/2sin(((5a+7a))⁄2)cos(((5a-7a))⁄2)
=> cos6a/sin6a
=>cot6a
Cheers!!
Regards,
Vikas (B. Tech. 4th year
Thapar University)

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