Difference between revisions of "Derivative/Definition"
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<center>[[Image:derivative1.PNG]]</center> | <center>[[Image:derivative1.PNG]]</center> | ||
| − | In the image above, the rate of change between the two points is the slope of the line that goes through them: <math>\frac{f(x+h)-f(x)}h</math>. | + | In the image above, the average rate of change between the two points is the slope of the line that goes through them: <math>\frac{f(x+h)-f(x)}h</math>. |
We can move the second point closer to the first one to find a more accurate value of the derivative. Thus, taking the [[limit]] as <math>h</math> goes to 0 will give us the derivative of the function at <math>x</math>: | We can move the second point closer to the first one to find a more accurate value of the derivative. Thus, taking the [[limit]] as <math>h</math> goes to 0 will give us the derivative of the function at <math>x</math>: | ||
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<center><math> f'(x) = \lim_{h\to 0}\frac{f(x+h)-f(x)}h. </math></center> | <center><math> f'(x) = \lim_{h\to 0}\frac{f(x+h)-f(x)}h. </math></center> | ||
| − | If this limit exists, it is the derivative of <math>f</math> at <math>x</math>. | + | If this limit exists, it is the derivative of <math>f</math> at <math>x</math>. If it does not exist, we say that <math>f</math> is not differentiable at <math>x</math>. |
== See also == | == See also == | ||
Revision as of 09:45, 17 November 2008
The derivative of a function is defined as the instantaneous rate of change of the function at a certain point. For a line, this is just the slope. For more complex curves, we can find the rate of change between two points on the curve easily since we can draw a line through them.
In the image above, the average rate of change between the two points is the slope of the line that goes through them: 
.
We can move the second point closer to the first one to find a more accurate value of the derivative. Thus, taking the limit as 
goes to 0 will give us the derivative of the function at 
:
If this limit exists, it is the derivative of 
at . If it does not exist, we say that is not differentiable at .
