Tan[45*(π/180)]

Tan[45  °]

Limit[Sin[x]/(x - π), x -> π]

(∂_x) (Sin[x]/x)

(∂_x) ((x^2) + x y + 2  y)

(∂_x) (Log[x y])

(∫_0^(2 π))(2*Sin[θ]*
            Cos[θ]) \[DifferentialD]θ

∫(1/(x - 1)) \[DifferentialD]x

∫(E^((x/2))) \[DifferentialD]x

∫Log[x] \[DifferentialD]x

(∑_(n = 1)^∞) (1/(2^n))