AB = \(\sqrt{(3-1)^2+(5-3)^2}\,=\,\sqrt{2^2+2^2}\,=\,\sqrt{4+4}\,=\,\sqrt8\)
BC = \(\sqrt{(3-1)^2+(3--1)^2}\,=\,\sqrt{2^2+4^2}\,=\,\sqrt{4+16}\,=\,\sqrt{20}\)
CD = \(\sqrt{(5-3)^2+(3--1)^2}\,=\,\sqrt{2^2+4^2}\,=\,\sqrt{4+16}\,=\,\sqrt{20}\)
DA = \(\sqrt{(5-3)^2+(5-3)^2}\,=\,\sqrt{2^2+2^2}\,=\,\sqrt{4+4}\,=\,\sqrt8\)
AB + BC + CD + DA = √8 + √20 + √20 + √8 ≈ 14.6
AB = \(\sqrt{(3-1)^2+(5-3)^2}\,=\,\sqrt{2^2+2^2}\,=\,\sqrt{4+4}\,=\,\sqrt8\)
BC = \(\sqrt{(3-1)^2+(3--1)^2}\,=\,\sqrt{2^2+4^2}\,=\,\sqrt{4+16}\,=\,\sqrt{20}\)
CD = \(\sqrt{(5-3)^2+(3--1)^2}\,=\,\sqrt{2^2+4^2}\,=\,\sqrt{4+16}\,=\,\sqrt{20}\)
DA = \(\sqrt{(5-3)^2+(5-3)^2}\,=\,\sqrt{2^2+2^2}\,=\,\sqrt{4+4}\,=\,\sqrt8\)
AB + BC + CD + DA = √8 + √20 + √20 + √8 ≈ 14.6