AsSingleFraction

This expression written as a single fraction: one numerator over one denominator, with
nothing divided inside either, as a + b/c is written (a c + b)/c. Any
expression, functions included, and nothing cancelled or multiplied out, so the factors
of the denominator stay as they were: 1/(t^2 + 1) + 1/(t + 1) is
(2 + t + t^2) / ((t^2 + 1)(t + 1)), and x/x stays x/x. The common
denominator is the least common multiple of the denominators as they are written, so
1/x + 1/x^2 is (x + 1)/x^2; nothing is factorised to find it. A rational number
counts as the fraction it is written as, so 2/3 + x/2 is (4 + 3x)/6. An
expression with no division in it comes back as it was. Dividing by a fraction moves
its denominator into the numerator, and the expression has no value where that
denominator is zero, so the answer says so: 1/(1/x) is x provided not x = 0.

Console.WriteLine("sin(x) + 1/cos(x)".ToEntity().AsSingleFraction());

(1 + cos(x) * sin(x)) / cos(x)