A drawing of the kite would be:
We have to find the diagonal which is the dashed line. To do it we can use pyhtagorean theorem by dividing the kite in right triangles and finding their heights. Finally, adding these heights to find the diagonal.
[tex]\begin{gathered} b=\sqrt[]{10^2-8^2} \\ b=\sqrt[]{100-64} \\ b=\sqrt[]{36} \\ b=6 \end{gathered}[/tex][tex]\begin{gathered} b=\sqrt[]{17^2-8^2} \\ b=\sqrt[]{289-64} \\ b=\sqrt[]{225} \\ b=15 \end{gathered}[/tex]
The diagonal is:
[tex]d=15+6=21[/tex]
