Sphere in 3-D
three parameters: (r, θ, φ) $x = r \cdot sin(φ) cos(θ)$ $y = r \cdot sin(φ) sin(θ)$ $z = r \cdot cos(θ)$
Trigonometry
$\cos(θ) = \frac{x}{\sqrt{x^{2} + y^{2}}}$ $\sin(θ) = \frac{y}{\sqrt{x^{2} + y^{2}}}$ $\tan(θ) = \frac{y}{x}$
arcsin/arccos/arctan is the inverse. e.g. $\tan(45^{\circ}) = 1$ $\arctan(1) = 45^{\circ}$