This features contributes the "Math Expression" node for evaluating free form mathematical expression. The associated plugin uses source code of JEP 2.4.1, an open-source Java library for parsing and evaluating mathematical expressions, which is under the copyright of its respective authors. To retrieve the source code of the library, please go to the JEP website:
"http://www.singularsys.com/jep/index.html"
Extension 
KNIME Math Expression (JEP)
Included nodes & related workflows
Legal
Copyright by KNIME AG, Zurich, Switzerland
Update site information
KNIME Analytics Platform 4.3 Update Site, Version 4.3.0
http://update.knime.com/analytics-platform/4.3
In case you can’t install the extension via drag & drop, please check that the update site is activated.