@Section @Title { Introduction } @Begin @PP The Lout definitions for the @Code "@Eq" symbol are kept in a file called {@Code "eq"}, which you must include at the start of your document if eq.file @Index { @Code "eq" file } you want equations, like this: @ID @OneRow @Code { "@SysInclude { tab }" "@SysInclude { eq }" "@SysInclude { doc }" "@Doc @Text @Begin" "..." "@End @Text" } This shows what to do if you want both tables and equations, but you may leave out the line for tables if you don't want them. Files of definitions, like {@Code "tab"} and {@Code "eq"}, must be included before the setup file, but may be included in any order. Alternatively, if you are using your own setup file, you may place the include commands within it; the place to put them is clearly marked in all the standard setup files. @PP With the @Code "eq" file included, you may write @ID @Code "@Eq { ... }" at any point in your document, and the symbols of @Code "@Eq" will be available between the braces. Any symbols available outside continue to be available inside, which means that equations may be freely mixed with other symbols, without restriction. @PP Equations may appear within a paragraph of text, or they may be displayed. {@Code "@Eq"}'s job is to produce an object containing the equation; it neither knows nor cares where this equation goes. To get an equation within a paragraph, simply place @Code "@Eq { ... }" at the desired point. To prevent it spreading over two lines, use {@Code "@OneCol @Eq { ... }"}. To display an equation, use a display symbol like @Code "@IndentedDisplay" or @Code "@CentredDisplay" (Section {@NumberOf displays}). For example, @ID @Code "@CentredDisplay @Eq { int supp pi on 0 sin ` x = 0 }" produces @CentredDisplay @Eq { int supp pi on 0 sin ` x = 0 } There are also symbols for aligned and numbered displays, which are very commonly used with equations. These symbols are the subject of Section {@NumberOf mathdisplays}. @PP In this chapter we show the Lout input at the left, and its result at the right: @ID { @Code "@Eq { {x sup 2 + y sup 2} over 2 }" |7ct @Eq { {x sup 2 + y sup 2} over 2 } } Subsequent examples will omit the enclosing {@Code "@Eq { ... }"}. @End @Section