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please help me to find the solution of the following question : 1 - sec 8a / 1 - sec 4a

please help me to find the solution of the following question  : 1 - sec 8a / 1 - sec 4a

Grade:9

1 Answers

Arun
25750 Points
6 years ago
Dear Yuvraj
 
(1 – sec 8A) / (1 – sec 4A)

 = (sec 8A -1) / (sec 4A -1)
=> [(1 - cos 8A)/ cos 8A] / [(1 - cos 4A)/ cos 4A]
=> [2 sin² 4A / 2 sin² 2A] * [cos 4A / cos 8A]
=> [(2 sin 4A * cos 4A) * sin 4A / cos 8A] / [2 sin² 2A]

=> [(sin 8A / cos 8A) * sin 4A] / [2 sin² 2A]
=> tan 8A * (sin 4A / 2 sin² 2A)
=> tan 8A * (2sin 2A * cos 2A / 2 sin² 2A)
=> tan 8A * ( cos 2A / sin 2A)
=> tan 8A * cot 2A 

=> tan 8A / tan 2A 

 

Regards

Arun (askIITians forum expert)

 

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