In the world of mathematics, integration is a powerful tool used to find the area under a curve. While the general formula for integration is ∫f(x)dx, there are two special cases that require unique approaches - functions in the form e^x and 1/x. Let's take a deeper look at these functions and their integration rules.

If we recall, the derivative of e^x is simply e^x. However, for functions that do not fall under this form, integration becomes more complex. The integral of a function is essentially the opposite of its derivative - if we integrate and then differentiate, we should end up with the original function. For instance, if we have f(x) = e^x, then the derivative is also e^x. Thus, the integral of e^x is ∫e^x dx = e^x + c, where c is the constant of integration.

It is worth noting that this concept also works in the reverse. If we integrate first and then differentiate, we will still end up with the original function.

The derivative of ln x is 1/x, therefore the integral of 1/x is ln x + c. In the case of a number multiplied by 1/x, such as 2/x, we simply multiply ln x by that number. For example, the integral of 2/x would be 2ln x + c.

From time to time, we may encounter functions that are a combination of e^x and 1/x, like e^x/x. While it may seem like we can integrate this function by combining the integration rules for e^x and 1/x, it is not as straightforward. In fact, the integral of this function - known as the Exponential Integral - cannot be calculated exactly and is represented by the symbol EI(x).

To sum it up:

- The integral of e^x is e^x + c
- The integral of 1/x is ln x + c
- The integral of e^x/x is EI(x)

When it comes to integrating special functions like e^x and 1/x, there are a few important things to remember:

- The integral of e^x is e^x + c
- The integral of 1/x is ln x + c
- The integral of any number multiplied by 1/x is that number multiplied by ln x + c
- The integral of a function that combines e^x and 1/x cannot be determined exactly and is represented by EI(x)

Now that we understand the rules for integrating these special functions, we can confidently approach any integration problem that comes our way. Happy integrating!

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