If a quadrilateral is a parallelogram, then its opposite sides are congruent therefore:
[tex]\begin{gathered} GH\cong JI \\ and \\ GJ\cong HI \end{gathered}[/tex]
Using the distance formula:
[tex]\begin{gathered} GH=\sqrt[]{(5-1)^2+(3-1)^2} \\ GH=\sqrt[]{16+4} \\ GH=\sqrt[]{20} \\ JI=\sqrt[]{(0-4)^2+(3-5)^2} \\ JI=\sqrt[]{16+4} \\ JI=\sqrt[]{20} \\ GH\cong JI \end{gathered}[/tex][tex]\begin{gathered} GJ=\sqrt[]{(0-1)^2+(3-1)^2} \\ GJ=\sqrt[]{1+4} \\ GJ=\sqrt[]{5} \\ HI=\sqrt[]{(4-5)^2+(5-3)^2} \\ HI=\sqrt[]{1+4} \\ HI=\sqrt[]{5} \\ GJ\cong HI \end{gathered}[/tex]
Step 2:
The diagonals are given by:
[tex]\begin{gathered} JH=\sqrt[]{(0-5)^2+(3-3)}^2 \\ JH=\sqrt[]{25} \\ JH=5 \\ GI=\sqrt[]{(4-1)^2+(5-1)^2} \\ GI=\sqrt[]{9+16} \\ GI=\sqrt[]{25} \\ GI=5 \\ JH=GI \\ 5=5 \\ so\colon \\ JH\cong GI \end{gathered}[/tex]
