How students enter algebraic expressions
In general, students can enter expressions in a format that is natural, with a slash (/) to indicate division or fractions, an asterisk (*) to indicate multiplication, parentheses for grouping, and a caret (^) to indicate exponentiation.
Examples

sin(2x^(y+z)) is interpreted as

sqrt((2H)/g) is interpreted as
Math palette for expression questions
If you deliver an expression question in which the math palette is enabled for students, students are able to use the palette to format their responses.
Parsing and evaluation
Learning Catalytics uses R (The R Project for Statistical Computing) to parse and evaluate algebraic expressions that students enter in response to an expression question. In general, most syntax that is valid in R is also valid in Learning Catalytics. The main exception is that Learning Catalytics assumes that all variables are only one letter (with N and n considered different variables); this way, a student can enter 2xy and it is interpreted as 2*x*y. Students can also use common functions: sin, cos, tan, arccos, arcsin, arctan, log, ln, and sqrt.