Prove f(x)=x+sin(x)f(x) = x + \sin(x)f(x)=x+sin(x) is strictly increasing.
f′(x)=1+cos(x)≥0f'(x) = 1 + \cos(x) \ge 0f′(x)=1+cos(x)≥0 everywhere
Not a polynomial
sin(x)\sin(x)sin(x) dominates
f′f'f′ can be negative