Given the right triangle:
Where a is the short side. Then, using the definition of the sine function:
[tex]\sin30\degree=\frac{a}{10}[/tex]But we know that:
[tex]\sin30\degree=\frac{1}{2}[/tex]Finally:
[tex]\begin{gathered} \frac{1}{2}=\frac{a}{10} \\ \\ \Rightarrow a=\frac{10}{2} \\ \\ \therefore a=5 \end{gathered}[/tex]