Question

The set of solution satisfying inequality cos x > 0 is

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Answer 1

Answer:

cos2x+cosx≥0

⇒2cos2x−1+cosx≥0

⇒(cosx+1)(2cosx−1)≥0

⇒cosx≤−1orcosx≥21

In (−π,π), −3π≤x≤3π 

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Answer 2

Answer:

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