Equivalent Expressions Calculator

Enter two expressions and this says whether they are equivalent. Both sides are expanded into a canonical sum of terms with exact fractions, so matching forms are a proof that the two agree everywhere rather than a sample of points that happened to agree, and a mismatch comes back with the difference polynomial and a value where they disagree. A second action takes one expression and up to four options and marks which of them match, which is the shape the question usually arrives in. It handles several variables, brackets, whole-number powers and division by a number; square roots, trigonometric functions, logarithms and division by an expression carrying a variable are refused rather than guessed at.