Definition:Elementary Function

An elementary function is one of the following:
 * 1) The constant function: $$f_c \left({x}\right) = c$$ where $$c \in \mathbb{R}$$;
 * 2) Powers of $$x$$: $$f \left({x}\right) = x^y$$, where $$y \in \mathbb{R}$$;
 * 3) Exponentials: $$f \left({x}\right) = e^x$$;
 * 4) Logarithms: $$f \left({x}\right) = \ln x$$;
 * 5) Trigonometrical functions: $$f \left({x}\right) = \sin x$$, $$f \left({x}\right) = \cos x$$;
 * 6) Inverse trigonometrical functions $$f \left({x}\right) = \sin^{-1} x, f \left({x}\right) = \cos^{-1} x$$;
 * 7) All functions obtained by replacing $$x$$ with any of the functions above, e.g. $$f \left({x}\right) = \ln \sin x, f \left({x}\right) = e^{\cos x}$$;
 * 8) All functions obtained by adding, subtracting, multiplying and dividing any of the above types any finite number of times.