While dedicated InDesign math plugins are typically premium products, you can access mathematical typesetting for free through native features and "lite" versions of professional tools. Native Math Expressions (No Plugin Required)

Each of these free math plugins has its features and limitations. Here's a brief overview:

usually outweighs the cost. However, for a budget-conscious creator, the most robust "free" path is

If you need to typeset advanced calculus (fractions with integrals), download EasyMath Lite. The ability to type \fracxy and get a formatted fraction is worth its weight in gold, even in the free version.

If you are opening files created by someone else using the paid MathTools plugin, you do not need to buy the plugin just to view the equations. You can download the InMath READER for free.

How to access: Go to Window > Math Expressions and select Insert MathML.

Akshay