When you use Math Assistant in OneNote, you'll notice that the Select an action dropdown beneath the equation changes depending on your selected equation. Here are some of the problem types supported depending on the equation you're trying to solve.
Note: This feature is only available if you have an Office 365 subscription. If you are an Office 365 subscriber, make sure you have the latest version of Office.
Arrays

For a list of real numbers, all of the below are supported.


Expressions 
For any expression, the available actions are:

Equations and inequalities 
For equations and inequalities, the following actions are available:

Systems 
It is important to have an equal number of equations and variables to ensure the correct functions are available. Systems can be written in two different ways:

Derivatives and integrals 
Derivatives can be written either with d/dx before the function, or with a prime mark.

Matrices 
Matrices can be written with square or round brackets. The following actions are supported for matrices:

Graphing in polar coordinates 
To graph a function in polar coordinates, r needs to be expressed as a function of theta.

Complex mode 
Note: Select Settings to switch between real numbers and complex numbers. For complex expressions and numbers containing imaginary unit i, the following actions are available.

See also
Create math equations using ink or text with Math Assistant in OneNote
Solve equations with Math Assistant in OneNote
Draw graphs of math functions with Math Assistant in OneNote