P2+Q2\mathrm{P}^{2}+\mathrm{Q}^{2}P2+Q2
P2+Q2\sqrt{\mathrm{P}^{2}+\mathrm{Q}^{2}}P2+Q2
P−Q\mathrm{P}-\mathrm{Q}P−Q
P+QP+QP+Q