# Fractions

To complete our ability to typeset basic math expressions, we should find out how to render fractions.

Fractions are on a separate page as, unlike the previous math commands we used, they require parameters. This is necessary because fractions have two parts - a numerator and denominator - and we must specify which is which.

## Fractions

To type a fraction, we use a command with two parameters: one for the numerator and one for the denominator.

Fractions are typeset with \frac{}{}

The first group contains the numerator. The second group contains the denominator.

### Exercise 5.1.1

Paste the code below into your project and compile the preview. What happens?

Then, correct the code to typeset the fraction 12/17.

$$\frac12 17$$

### Solution 5.1.1

When the given code is compiled, the result looks like the fraction 1/2 followed by 17. This is because the command \frac took the first object following it, 1, as the numerator, and the second object 2 as the denominator.

In order to properly type the fraction 12/17, we must use curly braces to group the numerator and denominator.

$$\frac{12}{17} \ ) ## Display style If you change the previously typeset fraction into display math mode, you can see that the inline version is significantly smaller. Inline fractions can be difficult to read, especially when there are more complex expressions in the numerator or denominator. For example, try adding the following sentence into your project, and compile the preview. The function \( f(x) = \frac{1}{x^2 + 1}$$ is continuous everywhere.

The denominator looks a bit cramped, right?

The function $f(x) = \frac{1}{x^2 + 1}$ is continuous everywhere.

Now, the function expression certainly looks better. However, the line breaks and changing alignment have annoyingly broken our sentence up.

Happily, there is a way to get the larger fraction from display mode at the same position inline.

The \displaystyle command makes inline math the same size as display math.

Try adding the command \displaystyle to the beginning of the inline math expression:

The function $$\displaystyle f(x) = \frac{1}{x^2 + 1}$$ is continuous everywhere.

Success! The math stays in its same inline position, but the fraction is now in display size.

Note that since normal letters and numerals do not change size in display mode, the f(x) part of the expression does not change - only the fraction.

On the next page, we will study some more commands which require parameters.