• Cancel[expr] cancels out common factors in the numerator and denominator of expr.
• Example: Cancel[(x^2-1)/(x-1)]
• Cancel cancels out the greatest common divisor of the numerator and denominator.
• Cancel[expr, Modulus->p] generates a result modulo p.
• Cancel[expr, Extension->Automatic] allows operations to be performed on algebraic numbers in expr.
• Cancel[expr, Trig -> True] treats trigonometric functions as rational functions of exponentials, and manipulates them accordingly.
• New in Version 1; modified in 3.