To graph the natural logarithm function, without using a calculator, and using a short table of easy points, we can proceed as follows:
1. We need to remember that the logarithm function is not defined for negative numbers. We cannot find any exponent that raised to a positive number that result in a negative number.
2. The logarithm function is not defined for x = 0. Therefore, we will have an asymptote at x = 0. It is a vertical asymptote, x = 0.
3. The value for ln(1) = 0, and we also know that the value of ln(e) = 1.
We need to remember that e is, approximately, 2.7182818284...
Now, using this information, we will have the following table:
x - values ---------- y-values
Negative values ---- the function is not defined
0 ------------- The function has a vertical asymptote
1 ------------- 0
e (approx. 2.72) ------------ 1
We can see the table of these values in the following drawing:
Now we can sketch a graph of this function as follows:
The domain of the natural logarithm function is, in interval notation:
And the range is (in interval notation too) as follows: