MathType

MathType screenshots

Write complex equations while using dozens of available symbols and functions.
MathType 6.7 : Functions Recognized

Alternative downloads

Mathpix Snipping Tool
2.7.1
FREE
Uses OCR to convert math equations from the screen into LaTex code.
Infinite Algebra 2
2.06.10
Infinite Algebra 2 app covers all typical Algebra material.
OpenOffice.org Math
3.3.0
FREE
OpenOffice.org Math - Create equations and formulas for your documents.