Question

Consider the following statements :
1. The function $$f\left( x \right) = $$  greatest integer $$ \leqslant x,\,x\, \in \,R$$   is a continuous function.
2. All trigonometric function are continuous on $$R.$$
Which of the statements given above is/are correct ?

A. 1 only
B. 2 only
C. Both 1 and 2
D. Neither 1 nor 2  
Answer :   Neither 1 nor 2
Solution :
Here, greatest integer function $$\left[ x \right]$$ is discontinuous at its integral value of $$x,\,\cot \,x$$   and $${\text{cosec}}\,x\,$$  are discontinuous at $$0,\,\pi ,\,2\pi $$   etc. and $$\tan \,x$$   and $$sec \,x$$  are discontinuous at $$x = \frac{\pi }{2},\,\frac{{3\pi }}{2},\,\frac{{5\pi }}{2}$$   etc. Therefore the greatest integer function and all trigonometric function are not continuous for $$x\, \in \,R$$
Therefore, neither (1) nor (2) are true.

Releted MCQ Question on
Calculus >> Continuity

Releted Question 1

For a real number $$y,$$ let $$\left[ y \right]$$ denotes the greatest integer less than or equal to $$y:$$ Then the function $$f\left( x \right) = \frac{{\tan \left( {\pi \left[ {x - \pi } \right]} \right)}}{{1 + {{\left[ x \right]}^2}}}$$     is-

A. discontinuous at some $$x$$
B. continuous at all $$x,$$ but the derivative $$f'\left( x \right)$$  does not exist for some $$x$$
C. $$f'\left( x \right)$$  exists for all $$x,$$ but the second derivative $$f'\left( x \right)$$  does not exist for some $$x$$
D. $$f'\left( x \right)$$  exists for all $$x$$
Releted Question 2

The function $$f\left( x \right) = \frac{{\ln \left( {1 + ax} \right) - \ln \left( {1 - bx} \right)}}{x}$$       is not defined at $$x = 0.$$  The value which should be assigned to $$f$$ at $$x = 0,$$  so that it is continuous at $$x =0,$$  is-

A. $$a-b$$
B. $$a+b$$
C. $$\ln a - \ln b$$
D. none of these
Releted Question 3

The function $$f\left( x \right) = \left[ x \right]\cos \left( {\frac{{2x - 1}}{2}} \right)\pi ,\,\left[ . \right]$$      denotes the greatest integer function, is discontinuous at-

A. all $$x$$
B. All integer points
C. No $$x$$
D. $$x$$ which is not an integer
Releted Question 4

The function $$f\left( x \right) = {\left[ x \right]^2} - \left[ {{x^2}} \right]$$    (where $$\left[ y \right]$$ is the greatest integer less than or equal to $$y$$ ), is discontinuous at-

A. all integers
B. all integers except 0 and 1
C. all integers except 0
D. all integers except 1

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Continuity


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