RedCrab is free software and simple to learn math. I think more suitable to say as a complete scientific calculator.
Before I ever write an article about Microsoft Mathematics: Microsoft Mathematics 4.0: easy to learn mathematics and the rival: MatheAss: Microsoft Mathematics rival. Microsoft Mathematics is free software developed by Microsoft that allows you to assist in solving problems related to mathematics. But MatheAss is a paid math software.
Sometime later I get a chance to try RedCrab. And see the screenshots that I got. Some people call it as a sophisticated scientific calculator. I also agree, except that is more simpler than the Microsoft Mathematics.
Besides the difference in terms of facilities and completeness of the various formulas in it, is also more difficult to use. I can not immediately use it when the first try. May need some adjustments.
In general is very interesting and helpful in solving math problems.