Hölder's Inequality for Finite Sums/Euclidean Plane

Hölder's Inequality for Sums: Euclidean Plane
In the context of a Euclidean plane, Hölder's Inequality for Sums takes the following form:


 * $x_1 y_1 + x_2 y_2 \le \paren {\size {x_1}^p + \size {x_2}^p}^{1 / p} \paren {\size {y_1}^q + \size {y_2}^q}^{1 / q}$

where:
 * $p, q > 1$
 * $\dfrac 1 p + \dfrac 1 q = 1$