I use OneNote as my virtual notepad. I love being able to have my notes in whatever type of office doc, pdf, etc. sync'd and available in my SkyDrive.
I recently had an issue with math notes that caused Mathematica1 font to display as a unknown character (small rectangle which is the default character when an app cannot find the font) as seen in here.
(There is also a 2010 version) with these wonderful features:
- Compute standard mathematical functions, such as roots and logarithms.
- Compute trigonometric functions, such as sine and cosine.
- Find derivatives and integrals, limits, and sums and products of series.
- Perform matrix operations, such as inverses, addition, and multiplication.
- Perform operations on complex numbers.
- Plot 2-D graphs in Cartesian and polar coordinates.
- Plot 3-D graphs in Cartesian, cylindrical, and spherical coordinates.
- Solve equations and inequalities.
- Calculate statistical functions, such as mode and variance, on lists of numbers.
- Factor polynomials or integers.
- Simplify or expand algebraic expressions.