If the logarithmic function is one-to-one,
its inverse exits. The inverse of a logarithmic function is
an exponential function. When you graph both the logarithmic
function and its inverse, and you also graph the line y = x,
you will note that the graphs of the logarithmic function and
the exponential function are mirror images of one another with
respect to the line y = x. If you were to fold the graph along
the line y = x and hold the paper up to a light, you would note
that the two graphs are superimposed on one another. Another
way of saying this is that a logarithmic function and its inverse
are symmetrical with respect to the line y = x.
Problem 2: Find the inverse, if it exists, to the function
If it does not exist, indicated the restricted domain where it will
exist and find the inverse on the restricted domain..
Solution: You can tell from the graph that the function is not
one-to-one. Part of the graph is located to the right of x =
6 and part of the graph is located to the left of x = 2. Therefore,
the inverse does not exists on the function's existing domain.
We will need to restrict the domain.
can be written
It can be simplified to
for all real numbers greater than 6. Therefore, if we restrict the
domain to all real numbers greater than 6, f(x) will have an inverse
whose range is all real numbers greater than 6.
provided x is greater than 6. The exponential function will have base
Which one do we choose?
We restricted the domain of the original function to the set of real numbers greater than 6. We also know that the range of the inverse is also the set of real numbers greater than 6.
Therefore, is the inverse because
If you would like to work another problem, click on Problem.
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Author: Nancy Marcus