Can someone please explain to me in simple wording what log function does as this is not clear to me at all:

source: http://www.cplusplus.com/reference/clibrary/cmath/log/

By seeing example code on that page i can't observe any logical relation from output number given the input. I want to be able to understand what this function actually do.

Thank you for your time.

Returns the natural logarithm of x. |

source: http://www.cplusplus.com/reference/clibrary/cmath/log/

By seeing example code on that page i can't observe any logical relation from output number given the input. I want to be able to understand what this function actually do.

Thank you for your time.

If you have the equation *x = b*^{y} then y is the logarithm of x to base b. The natural logarithm just means that the base is e http://en.wikipedia.org/wiki/E_%28mathematical_constant%29

There is also a function named log10 that use base 10.

There is also a function named log10 that use base 10.

I am sorry but i am just stupid and still not get it.

wiki:

e = 2.71828

How can something have decimal as a base.

I can understand base 10 base 2 and 16

but how base can be 2.7.....???

1. log10 expects some number for parameter (that its base is 10)?

2. log expect number (where base is 2.718....) ?

3. log2 ... (base 2)?

The natural logarithm just means that the base is e |

wiki:

e = 2.71828

How can something have decimal as a base.

I can understand base 10 base 2 and 16

but how base can be 2.7.....???

1. log10 expects some number for parameter (that its base is 10)?

2. log expect number (where base is 2.718....) ?

3. log2 ... (base 2)?

When you have an exponentiation on the form *b*^{y}, b is called the base and y is called the exponent. What the log functions returns is the exponent. Don't confuse the word *base* with how it's used when talking about numeral systems (hex, dec, etc.). They mean different things.

It's just a matter of solving the equation.

x = 10^{y}

y = log10(x)

x = 2^{y}

y = log2(x)

x = e^{y}

y = log(x)

These equations are usually not easy to solve by hand so that's why we can use the functions. As you probably have noticed we don't have a log function for arbitrary bases, so it's a hard problem to solve efficiently even for a computer.

It's just a matter of solving the equation.

x = 10

y = log10(x)

x = 2

y = log2(x)

x = e

y = log(x)

These equations are usually not easy to solve by hand so that's why we can use the functions. As you probably have noticed we don't have a log function for arbitrary bases, so it's a hard problem to solve efficiently even for a computer.

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