SpeQ is a small, extensive mathematics program with a simple, intuitive interface

SpeQ Mathematics
Free
Offline
http://www.speqmath.com/index.php?id=1

SpeQ Mathematics is a free math software for your computer. With the help of this freeware you can easily learn math and solve complex problems in mathematics. It has inbuilt support for a wide variety of variables, constants and mathematical functions. SpeQ Mathematics also lets you define functions and custom variables. You can also solve problems of trigonometry by using this freeware.