Add link to SQLite docs on built-in math functions

Author: lggruspe

README.md

@@ -172,7 +172,7 @@ go build --tags "icu json1 fts5 secure_delete"
 |  International Components for Unicode | sqlite_icu | This option causes the International Components for Unicode or "ICU" extension to SQLite to be added to the build |
 | Introspect PRAGMAS | sqlite_introspect | This option adds some extra PRAGMA statements. <ul><li>PRAGMA function_list</li><li>PRAGMA module_list</li><li>PRAGMA pragma_list</li></ul> |
 | JSON SQL Functions | sqlite_json | When this option is defined in the amalgamation, the JSON SQL functions are added to the build automatically |
-| Math Functions | sqlite_math_functions | This compile-time option enables built-in scalar math functions | 
+| Math Functions | sqlite_math_functions | This compile-time option enables built-in scalar math functions. For more information see [Built-In Mathematical SQL Functions](https://www.sqlite.org/lang_mathfunc.html) |
 | Pre Update Hook | sqlite_preupdate_hook | Registers a callback function that is invoked prior to each INSERT, UPDATE, and DELETE operation on a database table. |
 | Secure Delete | sqlite_secure_delete | This compile-time option changes the default setting of the secure_delete pragma.<br><br>When this option is not used, secure_delete defaults to off. When this option is present, secure_delete defaults to on.<br><br>The secure_delete setting causes deleted content to be overwritten with zeros. There is a small performance penalty since additional I/O must occur.<br><br>On the other hand, secure_delete can prevent fragments of sensitive information from lingering in unused parts of the database file after it has been deleted. See the documentation on the secure_delete pragma for additional information |
 | Secure Delete (FAST) | sqlite_secure_delete_fast | For more information see [PRAGMA secure_delete](https://www.sqlite.org/pragma.html#pragma_secure_delete) |