Application of Derivatives 4 Question 28

####29. If p,q and r are any real numbers, then

(a) max(p,q)<max(p,q,r)

(1982,1M)

(b) min(p,q)=12(p+q|pq|)

(c) max(p,q)<min(p,q,r)

(d) None of the above

Objective Questions II

(One or more than one correct option)

 30. If f(x)=cos(2x)cos(2x)sin(2x)cosxcosxsinx, then sinxsinxcosx

(2017 Adv.) (a) f(x) attains its minimum at x=0

(b) f(x) attains its maximum at x=0

(c) f(x)=0 at more than three points in (π,π)

(d) f(x)=0 at exactly three points in (π,π)

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Answer:

Correct Answer: 29. (a, b)

Solution:

  1. Since, max(p,q)=p, if p>q

q, if q>p

p, if p is greatest.

and max(p,q,r)=q, if q is greatest.

r, if r is greatest.

max(p,q)<max(p,q,r) is false.

We know that, |pq|=pq, if pqqp, if p<q

=q, if pqp, if p<q

12p+q|pq|=min(p,q) cos2xcos2xsin2x



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