Fixed function exponentiation not being parsed correctly

[MadScientistBR]

Problem

sec2(x)** and sec^2(x) were treated as invalid. Therefore, the users had to manually write sec(x)^2 to get sec^2(x).

Turns out this was a SymPy parser configuration issue: the function_exponentiation transformation, which rewrites f**n(x) as f(x)**n, isn't enabled by default and has to be explicitly included.

Changes

• app/utility/expression_utilities.py: We explicitly pass the function_exponentitation transformation to the SymPy parser in function parse_expression (line 813 and 815).
• app/tests/symbolic_evaluation_test.py: added test cases covering all supported trig/hyperbolic functions.

Closes issue #257.

[m-messer]

Thanks, @MadScientistBR, for the contribution. I ran the change against our dataset (https://github.com/lambda-feedback/compareExpressions/actions/runs/30247364907). The 50 network errors are from AWS blocking parallelised requests, and the remaining 36 errors are unrelated to this change.

@peterbjohnson, I have reviewed the change, and it is well implemented. I have also tested it on the platform, and the elementary functions when squared, such as sec^2(x) and sin^2(x), all preview and evaluate correctly.

[peterbjohnson]

Fantastic work, thank you for the contribution!