- A6
- B9
- C8
- D7
View written solutionFree
Correct answer: C
- Given function
We need to study
where is the greatest integer function.
We must find:
- = number of points where is not continuous
- = number of points where is not differentiable
Then compute .
- Where can problems occur?
The function is a sum of two parts:
- , which is discontinuous at every integer
- , which is continuous everywhere but not differentiable at
So possible special points in the interval are the integers inside it:
and also because of the modulus corner.
- Continuity analysis
(i) Continuity of
The greatest integer function has jump discontinuity at every integer. Thus in , discontinuities occur at
(ii) Continuity of
This is continuous for all real , including .
Therefore, the sum is discontinuous exactly at
So,
- Differentiability analysis A function can be differentiable only where it is continuous. Hence all discontinuity points are automatically non-differentiable.
So is not differentiable at least at
Now check whether there are any additional non-differentiable points.
(i) For
Between consecutive integers, is constant, so differentiable there with derivative .
(ii) For
It is not differentiable at
but is already included above.
Thus there is no extra point besides the discontinuity points. Hence,
- Compute
- Option check
The correct option is
which is Option C.
- Comparison with stored answer
Stored correct answer: C
Our derived answer: C
So they agree.
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