Natural Logarithm - ln(x)
Natural logarithm is the logarithm to the base e of a number.
Definition of natural logarithm
When
e y = x
Then base e logarithm of x is
ln(x) = loge(x) = y
The e constant or Euler's number is:
e ≈ 2.71828183
Ln as inverse function of exponential function
The natural logarithm function ln(x) is the inverse function of the exponential function ex.
For x>0,
f (f -1(x)) = eln(x) = x
Or
f -1(f (x)) = ln(ex) = x
Natural logarithm rules and properties
| Rule name | Rule | Example |
|---|
Product rule | ln(x ∙ y) = ln(x) + ln(y) | ln(3 ∙ 7) = ln(3) + ln(7) |
Quotient rule | ln(x / y) = ln(x) - ln(y) | ln(3 / 7) = ln(3) - ln(7) |
Power rule | ln(x y) = y ∙ ln(x) | ln(28) = 8 ∙ ln(2) |
Ln of zero | ln(0) is undefined | |
 | |
Ln of one | ln(1) = 0 | |
Derivative | f (x) = ln(x) ⇒ f ' (x) = 1 / x | |
Integral | ∫ ln(x)dx = x ∙ (ln(x) - 1) + C | |
Derivative of natural logarithm (ln) function
The derivative of the natural logarithm function is the reciprocal function.
When
f (x) = ln(x)
The derivative of f(x) is:
f ' (x) = 1 / x
Integral of natural logarithm (ln) function
The integral of the natural logarithm function is given by:
When
f (x) = ln(x)
The integral of f(x) is:
∫ f (x)dx = ∫ ln(x)dx = x ∙ (ln(x) - 1) + C
Natural logarithms table
| x | ln x |
|---|
| 0 | undefined |
| 0+ | - ∞ |
| 0.0001 | -9.210340 |
| 0.0010 | -6.907755 |
| 0.0100 | -4.605170 |
| 0.1000 | -2.302585 |
| 1.0000 | 0.000000 |
| 2.0000 | 0.693147 |
| e ≈ 2.7183 | 1.000000 |
| 3.0000 | 1.098612 |
| 4.0000 | 1.386294 |
| 5.0000 | 1.609438 |
| 6.0000 | 1.791759 |
| 7.0000 | 1.945910 |
| 8.0000 | 2.079442 |
| 9.0000 | 2.197225 |
| 10.0000 | 2.302585 |
| 20.0000 | 2.995732 |
| 30.0000 | 3.401197 |
| 40.0000 | 3.688879 |
| 50.0000 | 3.912023 |
| 60.0000 | 4.094345 |
| 70.0000 | 4.248495 |
| 80.0000 | 4.382027 |
| 90.0000 | 4.499810 |
| 100.0000 | 4.605170 |
| 200.0000 | 5.298317 |
| 300.0000 | 5.703782 |
| 400.0000 | 5.991465 |
| 500.0000 | 6.214608 |
| 600.0000 | 6.396930 |
| 700.0000 | 6.551080 |
| 800.0000 | 6.684612 |
| 900.0000 | 6.802395 |
| 1000.0000 | 6.907755 |
| 10000.0000 | 9.210340 |
Natural logarithm calculator ►
See also