Q.

Let A(t)=[aij] is a matrix of order  3×3 given by aij={2cos t if i=j1 if   |ij|=1,       then 0 otherwise 

 Column-I Column-II
P)The number of t in interval [2π,4π]  such that  |A(t)|  =4 is equal to(1)0
Q)Aπ17A4π17  is equal to(2)1
R)The maximum value of |A(t)|+|A(2t)|,  tR is equal to(3)4
S)0π|A(t)A(4t)| dt is equal to(4)6
  (5)8

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a

P-5;  Q-4;   R-3;   S-1

b

P-3;   Q-2;   R-5;   S-1

c

P-3;   Q-4;   R-5;   S-1

d

P-1;   Q-2;   R-3;  S-4

answer is C.

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Detailed Solution

A(t)=2cost1012cost1012cost

|A(t)|=2cost(4cos2t1)2cost=8cos3t4cost             |A(t)|=4cost cos2t

(A)  |A(t)|=4t=2nπ,nIt=2π,0,2π,4π
(B)   |A(π17)||A(4π17)|=16cosπ17cos2π17cos4π17cos8π17 =sin16π16πsinπ17=1
(C)   |A(t)|+|A(2t)|=4cost  cos2t+4cos2t  cos4t8
(D)   0π16 cos t cos2t  cos4t  cos8tdt= 0πsin16tdtsint

= 0π/2(sin16tsint+sin(16π16t)sin(πt))dt=0

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