Basic Maths Grand Test- Q13

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Which of the above are CORRECT ?

A. Only (A)

B. (A) and (C)

C. (B) and (C)

D. (B) and (D)

asked Nov 18 in Basic Maths by gbmentor (85,520 points)
reshown Nov 20 by getgatebook

1 Answer

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f(x)=cos2x+cos4x

f^{'}(x)=0

(-sin2x*2)-(sin4x*4) =0

cos2x=\frac{-1}{4}

As you can see, there are 4 points in (-\Pi,\Pi) where cos2x=\frac{-1}{4}

And also f(x)=cos2x+cos4x attains its maximum value at x=0.

So option C.(B) and (C) is correct.

answered Nov 20 by tspranaykumar562 (2,720 points)
edited Nov 21 by tspranaykumar562
cos2x = -1/4
Answer:
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