Topic: Graphing Logarithms

How can you graph logarithms? For example, y = 2log (x-5)? Would i have to rearrange it to graph? Thanks in advance for the help.

Re: Graphing Logarithms

Insert function -> f(x) = 2*log(x-5)

3 (edited by pin 2010-11-20 15:12:21)

Re: Graphing Logarithms

Teito wrote:

... Would i have to rearrange it to graph? ...

If you like rearranging, why not?
You must know that logarithm of a negative number doesn't give a result as a real number. But you might know that log(-1) = i*pi/ln(10). So, your function can be rearranged:
2 log (x - 5) = 2 log [(-1) (5 - x)] = 2 i * pi/ln(10) + 2 log(5 - x)
for values x lower then 5.

It's difficult to plot three numbers - x, Re(y) and Im(y) - in 2D graph. Just for better imagination, a parametric function can be plotted, where original x input is replaced by t. As there is no scale for t values, only selected points of the function are shown, marked with corresponding original values of the input x.

I know, it doesn't look as a graph, it's only a demonstration. ;-)

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Attachment icon Log-graph.grf 5.08 kb, 369 downloads since 2010-11-20