我安装了 MacTex、Tex Live 实用程序并在 TexMaker 中编辑。
问题是我通过 Tex Live 安装了许多软件包（几乎全部），当我使用其中一些软件包时，例如：
序言部分使用 \usepackage{helvetic}，
Latex 输出为：
“未找到文件 helvetic.sty”。其他一些软件包也存在同样的问题。
为什么如果我通过 Tex Live 安装它们就会出现这种情况？
多谢！
答案1
这里有两个包的概念，它们是不一样的。
首先，TeX Live 有一个软件包的概念，例如helvetic。以下是 TeX Live Manager 对此的说明：
$ tlmgr info helvetic
package: helvetic
category: Package
shortdesc: URW "Base 35" font pack for LaTeX.
longdesc: A set of fonts for use as "drop-in" replacements for Adobe's basic set, comprising: - Century Schoolbook (substituting for Adobe's New Century Schoolbook); - Dingbats (substituting for Adobe's Zapf Dingbats); - Nimbus Mono L (substituting for Abobe's Courier); - Nimbus Roman No9 L (substituting for Adobe's Times); - Nimbus Sans L (substituting for Adobe's Helvetica); - Standard Symbols L (substituting for Adobe's Symbol); - URW Bookman; - URW Chancery L Medium Italic (substituting for Adobe's Zapf Chancery); - URW Gothic L Book (substituting for Adobe's Avant Garde); and - URW Palladio L (substituting for Adobe's Palatino).
installed: Yes
revision: 31835
sizes: run: 2377k
relocatable: Yes
cat-date: 2012-06-06 22:57:48 +0200
cat-license: gpl
collection: collection-fontsrecommended
其次，LaTeX 中有一个“包”，你可以使用以下方式加载到文档中
\usepackage{helvet}
在某些情况下，可能存在两种含义的包。但在其他情况下，则不存在。helvetic提供字体，但没有同名的 LaTeX 包，正如您所发现的。也就是说，helvetic与您在文档中使用这些字体所需的 LaTeX 包不同。helvet是您为此所需的 LaTeX 包。
helvet由 TeX Live 包提供psnfss：
$ tlmgr info psnfss
package: psnfss
category: Package
shortdesc: Font support for common PostScript fonts.
longdesc: Font definition files, macros and font metrics for freely- available Adobe Type 1 fonts. The font set consists of the 'LaserWriter 35' set (originally 'freely available' because embedded in PostScript printers), and a variety of other free fonts, together with some additions. Note that while many of the fonts are available in PostScript (and other) printers, most publishers require fonts embedded in documents, which requires that you have the fonts in your TeX system. Fortunately, there are free versions of the fonts from URW (available in the URW base5 bundle). The base set of text fonts covered by PSNFSS are: AvantGarde, Bookman, Courier, Helvetica, New Century Schoolbook, Palatino, Symbol, Times Roman and Zapf Dingbats. In addition, the fonts Bitstream Charter and Adobe Utopia are covered (those fonts were contributed to the Public Domain by their commercial foundries). Separate packages are provided to load each font for use as main text font. The packages helvet (which allows Helvetica to be loaded with its size scaled to something more nearly appropriate for its use as a Sans-Serif font to match Times) and pifont (which provides the means to select single glyphs from symbol fonts) are tailored to special requirements of their fonts. Mathematics are covered by the mathptmx package, which constructs passable mathematics from a combination of Times Roman, Symbol and some glyphs from Computer Modern, and by Pazo Math (optionally extended with the fpl small-caps and old-style figures fonts) which uses Palatino as base font, with the mathpazo fonts. The bundle as a whole is part of the LaTeX 'required' set of packages.
installed: Yes
revision: 33946
sizes: src: 73k, doc: 521k, run: 441k
relocatable: Yes
cat-version: 9.2a
cat-date: 2012-07-23 15:04:13 +0200
cat-license: lppl
collection: collection-latex