
# Write functions as pure math
cartesian(r, θ, ϕ) = r*cos(θ)*sin(ϕ), r*sin(θ)*sin(ϕ), r*cos(ϕ)

f(x) = 2x^2+5x-10
∇f(x) = 4x+5
∇²f(x) = 4

# Set notation are defined operators
10 ∈ [12,13,14,15] # returns false

