Insert and edit equations

You can put math in a document, from a quick x² in a sentence to a formula on a line of its own. You write each equation in LaTeX, the notation most math tools use, and a preview shows how it will look as you type.

You need edit access to insert or change an equation. On a phone, equations show in the document, but you can't insert or edit them. In a header or footer you can change an equation that's there, but you can't insert one.

Insert an equation

1. Place your cursor where the equation should go.
2. Open the Insert menu and choose Equation.
3. An empty equation appears at the cursor as a dashed box, and the Equation panel opens on the right with the cursor in its LaTeX field.
4. Type the equation, for example x^2 + y^2 = r^2. The preview at the top of the panel draws it as you type.
5. Press Cmd+Enter (Ctrl+Enter on Windows and Linux), or click outside the field. The equation is saved, and your cursor goes back to the document, right after the equation. Enter starts a new line in the field, which keeps long LaTeX readable and draws the same equation.

Leaving the field, for example by clicking back in the document, saves the equation too. Press Escape to throw away what you typed since the last save.

Write LaTeX

Eigen reads the common LaTeX math commands: \frac{a}{b} for a fraction, \sqrt{x} for a root, x_i and x^2 for scripts, \sum, \int, Greek letters such as \alpha, and environments such as cases and pmatrix. For quantum states, the bra-ket commands \bra{\phi}, \ket{\psi}, \braket{\phi|\psi}, \expval{A}, \mel{a}{A}{b} and \ketbra{a}{b} draw angle brackets and bars that grow with what's inside them. As in the physics package, \bra{\phi}\ket{\psi} and \braket{\phi}{\psi} join into one bracket.

Type a command's name and a space, and Eigen adds the braces it needs. \frac and a space becomes \frac{}{}, with the cursor in the first pair. An empty part of a fraction, a root, or another template shows as a dotted box in the preview, so you can see what's left to fill in.

If the LaTeX has a mistake, the field turns red and a message under it says what's wrong, with the spot underlined. The equation isn't saved until you fix it, and the preview shows the equation as it was last saved.

You can also paste MathML, starting with <math, into the field. Eigen reads it as the equation, and once it's saved the field shows its LaTeX.

Pick symbols from the menus

Above the LaTeX field are five buttons, each opening a grid of symbols, as in Google Docs:

• Greek letters (α)
• Miscellaneous operations (±)
• Relations (≤)
• Math operations (√): fractions, roots, scripts, brackets, sums, integrals, and limits
• Arrows (→)

Click a symbol to add it at the cursor in the field. A fraction, a root, or another template puts the cursor in its first empty slot.

Show an equation on its own line

An equation sits in the line of text by default. To give it a line of its own, centered, choose On its own line next to Style under Layout in the Equation panel, or right-click the equation and choose Style → On its own line. Choose In line with text to put the equation back in the text.

Change or remove an equation

Click an equation to select it and open its panel, then edit its LaTeX. To open the panel with the cursor in its LaTeX field, move onto the equation with the arrow keys and press Enter, or click the selected equation again. To remove an equation, select it and press Backspace or Delete.

Right-click an equation for Cut, Copy, Edit equation, which opens its panel with the cursor in the LaTeX field, Style, where a check marks In line with text or On its own line, Add comment, and, last and in red, Delete equation.

Other people see your changes once you save them, not while you type. If two people change the same equation, the last one saved wins.

Paste equations

Copy an equation from Word for the web, or from a web page that shows math, and paste it into a document. It comes in as an equation you can edit, in the line or on its own line as it was. When the page includes the equation's LaTeX, the LaTeX field shows it.

An equation copied from one Eigen document to another stays an equation, with its LaTeX. An equation copied from Google Docs pastes as plain text. So does one from some web pages, which draw their math without keeping a copy of it. Pasted into a comment, an email, or a text box on a slide, an equation comes in as one-line text, such as (a+b)/2. To bring in the equations of a Word file, import the file.

Comment on an equation

Right-click the equation and choose Add comment. Or click the equation, then press Cmd+Option+M (Mac) or Ctrl+Alt+M (Windows), or choose Comment from the Insert menu. The comment's Title starts as the equation's text. A commented equation shows a small triangle in the comment's color at its top-right corner. Click the triangle to open the comment. See Comment and discuss.

Equations in downloads and search

A Word download turns each equation into a Word equation, and a PDF or web page download draws it. See Export to Word, PDF, or HTML for what each format keeps.

Word count, searching your files, and a copy pasted as plain text read an equation in a one-line text form, such as x^2, (a+b)/2, or √(x+1). The find bar inside a document doesn't look inside equations.