Question

The function $$f\left( x \right) = \frac{{1 - \sin \,x + \cos \,x}}{{1 + \sin \,x + \cos \,x}}$$      is not defined at $$x = \pi .$$  The value of $$f\left( \pi \right),$$  so that $$f\left( x \right)$$  is continuous at $$x = \pi ,$$  is :

A. $$ - \frac{1}{2}$$
B. $$\frac{1}{2}$$
C. $$ - 1$$  
D. $$1$$
Answer :   $$ - 1$$
Solution :
$$\eqalign{ & f\left( x \right) = \frac{{2\,{{\cos }^2}\frac{x}{2} - 2\sin \frac{x}{2}\,\cos \frac{x}{2}}}{{2\,{{\cos }^2}\frac{x}{2} + 2\sin \frac{x}{2}\,\cos \frac{x}{2}}} \cr & = \frac{{\cos \frac{x}{2} - \sin \frac{x}{2}}}{{\cos \frac{x}{2} + \sin \frac{x}{2}}} \cr & = \tan \left( {\frac{\pi }{4} - \frac{x}{2}} \right){\text{ at }}x \cr & = \pi ,\,f\left( \pi \right) \cr & = - \tan \frac{\pi }{4} \cr & = - 1 \cr} $$

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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