Question 8
If cos (α + β) = 0, then sin (α – β) can be reduced to
(A) cos β (B) cos 2β (C) sin α (D) sin 2α
Given that
cos (α + β) = 0
cos (α + β) = cos 90°
Comparing angles
α + β = 90°
α = 90° − β
Now,
sin (α – β) = sin (90° − β − β)
= sin (90° − 2β)
Using cos A = sin (90° − A)
= cos 2β
So, the correct answer is (B)
Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.
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