Advanced Online Scientific Calculator
http://www.alcula.com/calculators/scientific-calculator/

An advanced scientific calculator which may be useful to students of mathematics and science. It’s distinguishing feature is that it stores numbers internally as fractions. All operations are performed, whenever possible using fraction values and the results are displayed as fractions, as well as in their floating point approximation. Another feature is the possibility to define an unlimited number of multi variable custom functions that can be used in expressions (custom functions are defined with the syntax ()= ex. myfunc(x,y)=(x^2+y^2)/2 ). The expression history can be edited and all results of the expressions that follow are automatically updated to reflect the changes. t is written using the Flex3 framework, so it’s a rather large file, certainly more suitable for broadband internet connections. This has been added to Student Research Resourcers Subject Tracer™ Information Blog. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog.