# Relationship between ln and exponential

### The logarithm and exponential functions

understand the relationship between the exponential function f(x) = ex and the natural logarithm function f(x) = ln x. Contents. 1. Exponential functions. 2. 2. It means that e x is a bijection from R onto (0, ∞), and that ln (x) is a bijection of (0, ∞) onto R. In other words, both functions pair up points in their domain. Here is the graph of the natural logarithm, y = ln x (Topic 20). Graph of b) What is the relationship between the graph of y = e x and the graph b) of y = e −x?.

When x is equal to zero, y is equal to one.

## Relationship between exponentials & logarithms: graphs

That's this point right over here. When x is equal to one, b to the one power or b to the first power is equal to four. Another way of thinking of this y or four is equal to b to the first power and actually we can do [said] must be four.

That's this point right over there. This point is telling us that b to the second power is equal to When x is equal to two, b to the second power, y is equal to Now we want to plot the three corresponding points on this function. Let me draw another table here. Now it's essentially the inverse function where this is going to be x and we want to calculate y is equal to log base b of x. What are the possibilities here? What I want to do is think Let's take these values because these are essentially inverse functions log is the inverse of exponents.

If we take the points one, four, and What is y going to be here? This is saying what power I need to raise b to to get to one. If we assume that b is non zero and that's a reasonable assumption because b to different powers are non zero, this is going to be zero for any non zero b.

This is going to be zero right there, over here. We have the point one comma zero, so it's that point over there.

### Logarithmic and exponential functions - Topics in precalculus

Notice this point corresponds to this point, we have essentially swapped the x's and y's. In general when you're taking an inverse you're going to reflect over the line, y is equal to x and this is clearly reflection over that line. Now let's look over here, when x is equal to four what is log base b of four.

What is the power I need to raise b to to get to four. In exact mode the base 10 logarithm of an integer is not evaluated because doing so would result in an approximate number. Turn on complex numbers if you want to be able to evaluate the base 10 logarithm of a negative or complex number.

## LOGARITHMIC AND EXPONENTIAL FUNCTIONS

Click the Simplify button. Algorithm for the base 10 logarithm function Click here to see the algorithm that computers use to evaluate the base 10 logarithm function. The natural logarithm function Background: You might find it useful to read the previous section on the base 10 logarithm function before reading this section.

The two sections closely parallel each other.

But why use base 10? After all, probably the only reason that the number 10 is important to humans is that they have 10 fingers with which they first learned to count. Maybe on some other planet populated by 8-fingered beings they use base 8!

In fact probably the most important number in all of mathematics click here to see why is the number 2. It will be important to be able to take any positive number, y, and express it as e raised to some power, x. We can write this relationship in equation form: How do we know that this is the correct power of e?

### Exponential and Logarithmic Equations

Because we get it from the graph shown below. Then we plotted the values in the graph they are the red dots and drew a smooth curve through them. Here is the formal definition. The natural logarithm is the function that takes any positive number x as input and returns the exponent to which the base e must be raised to obtain x. It is denoted ln x. Evaluate ln e 4.

**Natural Logarithms**

The argument of the natural logarithm function is already expressed as e raised to an exponent, so the natural logarithm function simply returns the exponent.

Express the argument as e raised to the exponent 1 and return the exponent. Express the argument as e raised to the exponent 0 and return the exponent. The domain of the natural logarithm function is all positive real numbers and the range is all real numbers. The natural logarithm function can be extended to the complex numbersin which case the domain is all complex numbers except zero.

The natural logarithm of zero is always undefined. Then finding x requires solving this equation for x: The natural logarithm function is defined to do exactly the opposite, namely: How to use the natural logarithm function in the Algebra Coach Type ln x into the textbox, where x is the argument. In floating point mode the natural logarithm of any number is evaluated.

In exact mode the natural logarithm of an integer is not evaluated because to do so would result in an approximate number. Turn on complex numbers if you want to be able to evaluate the natural logarithm of a negative or complex number. Algorithm for the natural logarithm function Click here to see the algorithm that computers use to evaluate the natural logarithm function.

You might find it useful to read the previous section on the natural logarithm function before reading this section. There we saw that it is possible to use the number e which is approximately 2.