Question Details

Let f : R R be a function defined by


f (x) = x2 sin ( π x2 ) ; if x 0 0 ; if x = 0

Then which of the following statements is TRUE?

Options

A

f ( x ) = 0 has infinitely many solutions in the interval [ 1 10 10 , )

B

f ( x ) = 0 has no solution in the interval [ 1 π , )

C

The set of solutions of f ( x ) = 0 in the interval ( 0 , 1 10 10 ) is finite

D

f ( x ) = 0  has more than  25  solutions in the interval ( 1 π 2 , 1 π ) '

Show Answer

Correct Answer :

Option D

f ( x ) = 0  has more than  25  solutions in the interval ( 1 π 2 , 1 π ) '

Solution :

The correct statement is that f(x)=0 has more than  25 solutions in the interval (1π2,1π).

Step-by-Step Explanation:

Step 1: Find the general condition for f(x)=0
For non-zero values of x, the function is defined as:

f(x)=x2sinπx2

Setting f(x)=0 for x0:

x2sinπx2=0sinπx2=0

Since sin()=0 when =kπ for any integer k:

πx2=kπ,kN+

Canceling π from both sides:

1x2=kx2=1kx=1k

Step 2: Determine the number of solutions in the interval (1π2,1π)
We need to find how many positive integer values of k satisfy:

1π2<1k<1π

Taking reciprocals reverses the inequality signs:

π<k<π2

Squaring all parts:

π2<k<π4

Step 3: Calculate the numerical range for k
Using the approximation π3.14159:

π29.87

π4=(π2)2(9.87)297.41

Therefore, the inequality becomes:

9.87<k<97.41

The integers k in this range are 10,11,12,,97.

The total count of these integers is:

97-10+1=88

Since 88>25, there are indeed more than 25 solutions in the interval (1π2,1π).

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