typo in a function name ...

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1560335 13f79535-47bb-0310-9956-ffa450edef68
improved javadoc

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1560336 13f79535-47bb-0310-9956-ffa450edef68