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Question
In the case, given below, find the value of angle A, where 0° ≤ A ≤ 90°.
sin (90° - 3A).cosec 42° = 1.
Solution
Sin (90° - 3A). cosec 42° = 1
⇒ sin (90° - 3A) = `(1)/("cosec" 42°)`
⇒ cos 3A = `(1)/("cosec" (90° - 48°)`
⇒ cos 3A = `(1)/(sec 48°)`
⇒ cos 3A = cos 48°
⇒ 3A = 48°
⇒ A = 16°.
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