I have an equation calling for the use of "log" and I don't really understand how to use it.

If X is b to the y, then y= log sub b (X)

Or so I recall.

And here is a concrete example, using base 10.

For example, the logarithm of 1000 to the base 10 is 3, because 3 is the number of 10s that must be multiplied together to get 1000: thus 10 × 10 × 10 = 1000;

Log 1000 = 3.

Source was Wikipedia article on logs.

You’ve misinterpreted the equation; it should be “61*log(Co/Ci)”, since log denotes the logarithm function. There is, in general, no easy to calculate the value by hand—use a scientific calculator.

That’s how the teacher presented it, I don’t know nothin’ bout no log.

Anyhoo, I dug out my graphing calculator and discovered the log button, so all is right in the world. Thanks. :)

The word “log” means “raised to what power?” The log is the exponent of some number (the base).

So, when you take the log base 10 of 100, that means 100 is 10 “raised to what power?” Since 10 ^ 2 =100, the log is the exponent, 2.

My algebra teacher used to make us say in class: “Logs are exponents!”

A logarithm is (sort of) the inverse function of exponentiation. Logarithms come in different bases (the number that is exponentiated) usually the function ‘log’ is assumed to be a logarithm of base ten (although any real or imaginary number can be used). The natural logarithm (denoted ‘ln’) is the logarithmic function of base e. e being the irrational Euler’s number.

Taking the log of a number gives the exponent that is required to raise the base to the given number; hence, “Logs are exponents!”