Hello all, i need to rearrange this formula to make E the subject (E=)
M= 0.67 log (0.37 E) +1.46
While i can rearrange most formula, the ones that contain log seem to confuse me.
Thanks in advance!
Hey Rpenguin.
To get rid of a log(x) term to get an x, you have the exponential of it. So as an example, if I have y = log(x) and I want to get x, then I take the exponential of both sides which gives exp(y) = exp(log(x)) = x which gives exp(y) = x.
Sorry to bother you again, Chiro, but if you were to enter this on a graphical calculator to find E how would you do this? Is there an "exp" button that i am missing? Just to compare answers, what value for E do you get if M = 9.5?
There are usually two types of logarithms: base 10 and base e. In terms of exponential, there is a button (usually its called e^x or exp(x)) and that will take the exponential in base e. If it's base ten then you simply calculate 10 to the power of the number to get the exponential in base 10.
Using a common computer package called R, I get the answer:
> (1/0.37)*exp((9.5-1.46)/0.67)
[1] E = 439877.81464595574653
If I use base 10 I get:
> (1/0.37)*10^((9.5-1.46)/0.67)
[1] 2702702702702.6914062
The reason I include base 10 is that unfortunately, sometimes people use log to mean log to the base 10 rather than to the natural base and it's a real pain in the neck when people say log(x) is log base 10 instead of log base e.
One thing though is that if you see ln(x) this is always base e no matter what.