\(C(0,3) \\
x_1=0 \\
y_1=3 \\ \\
D(4,7) \\
x_2=4 \\
y_2=7 \\ \\
\overset{\underline{\ \ \ \ }}{CD} =\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}=\sqrt{(4-0)^2+(7-3)^2}= \\
=\sqrt{4^2+4^2}=\sqrt{16+16}=\sqrt{16 \times 2}=4\sqrt{2} \\ \\
\boxed{\overset{\underline{\ \ \ \ }}{CD} = 4\sqrt{2}}\)
