the formula for the area of a triangle is
![A=b\cdot(h)/(2)](https://img.qammunity.org/2023/formulas/mathematics/high-school/39ui8mewhg73f0wgi2pvjn1izdem18lo4q.png)
then if we have a right triangle it would look like this
in a right triangle the base and the heigth are represented by the legs
using the leg given and the area we can find the other leg
![\begin{gathered} A=(b\cdot h)/(2) \\ 10=(4\cdot x)/(2) \\ 2\cdot10=4\cdot x \\ 4x=20 \\ x=(20)/(4) \\ x=5 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/t9equnwfy0kio7n8lbwpn2g8ixo4mryzxl.png)
the length of the other leg is 5 cm.