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Question
If Sec 4A = cosec (A – 20°) where 4A is an acute angle, find the value of A.
Solution
Sec 4A = sec [90 − 𝐴 − 20] [∵ sec(90 − θ) = cosec θ]
Sec 4A = sec (90 – A + 20)
Sec 4A = sec (110 – A)
4A = 110 – A
5A = 110
`A = 110/5 => A = 22`
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