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opendiscuss
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The slope of the graph of f(x) = x changes abruptly when x = 0. Does this
function have a derivative? If so, what is it? If not, why not?
Explanation is given in the course material, but not clear...Why cant the tangent line be defined at (0,0)...
 2 years ago
 2 years ago
opendiscuss Group Title
The slope of the graph of f(x) = x changes abruptly when x = 0. Does this function have a derivative? If so, what is it? If not, why not? Explanation is given in the course material, but not clear...Why cant the tangent line be defined at (0,0)...
 2 years ago
 2 years ago

This Question is Open

iisthphir Group TitleBest ResponseYou've already chosen the best response.1
The function is not continuous at 0 so the derivative can't be taken. The two sided limit as x > 0 does not exist. As the function is elsewhere linear, its derivative is constant. For x < o it is 1 for x > 0 it is 1.
 2 years ago

khoutir Group TitleBest ResponseYou've already chosen the best response.0
the function is continuous but hasn't a derivative because: \[\lim_{x \rightarrow 0}[f(x+\Delta x)f(x)/\Delta x] \neq \lim_{x \rightarrow +0}[f(x+\Delta x)f(x)/\Delta x] \] for x<0 we have :\[f(x+\Delta x)f(x)/\Delta x=[(x+\Delta x)+x]/\Delta x= 1\] for x>0 we get :\[f(x+\Delta x)f(x)/\Delta x=[(x+\Delta x)x]/\Delta x= 1\] so the limit of the difference quotient doesn't exist and so that the derivative at x=0
 2 years ago

JingleBells Group TitleBest ResponseYou've already chosen the best response.0
f(x)=x is continuous at x=0: \[f(x ^{})=\lim_{x \rightarrow 0}\left x \right=0\] \[f(x ^{+})=\lim_{x \rightarrow 0}\left x \right=0\] dw:1342611754796:dw However, \[f \prime(x)\] has a point of jump discontinuity at x=0: \[f \prime(0^{})=\lim_{x \rightarrow 0}1=1\] \[f \prime(0^{+})=\lim_{x \rightarrow 0}1=1\] dw:1342612014321:dw at x=0 left hand limit \[\neq \] righthand limit as Problem Set 1 Question 1D, 3 (d) and (e) demonstrate similar cases.
 2 years ago
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