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Question
If cos (α + β) = 0 then sin (α – β) = ?
Options
sin 2α
cos 2β
sin α
cos β
MCQ
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Solution
cos 2β
Explanation:
cos (α + β) = 0
⇒ cos (α + β) = cos 90°
⇒ α + β = 90°
⇒ α = (90° – β)
∴ (α – β) = (90° – β – β)
= (90° – 2β)
⇒ sin (α – β) = sin (90° – 2β)
= cos 2β
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