RRB Group D 13-Dec-2018 Shift 2 Solved Paper

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Question : 30 of 100

Marks: +1, -0

If

2cos^x-sin^2x=-0.25°

and

0°≤x≤90°

, then x=_____?

45°
30°
90°
60°

Solution:

2cos^2x-sin^2x=-0.25

2cos^2x-(x-cos^2x)=-0.25

3cos^2x=0.75

cos^2x=0.25

cosx=0.5=1/2

⇒x=60°

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