D[x^2 Log[x]  -  Cosh[x], x]

(∂_x)( (x^(2 )) Log[x]  - Cosh[x])

Integrate[1/Sqrt[x^2 + a^2], x]

∫(1/(Sqrt[(x^2) + (a^2)])) \[DifferentialD]x

Integrate[Sin[x]/x, x]

∫Sin[x]/x \[DifferentialD]x

(∫_0^1000000) Sin[x]/x \[DifferentialD]x

N[%]

Series[(f[x - h] + f[x + h] - 2 f[x])/h^2, {h, 0, 5}]