ANSWER
The length of the third leg is
STEP-BY-STEP EXPLANATION:
The figure given is a right-angled triangle.
To find the third length of the triangle, we need to apply Pythagora's theorem
It states that
[tex]\begin{gathered} (Hypotenuse)^2=(opposite)^2+(adjacent)^2 \\ \end{gathered}[/tex]The third length of the triangle is the hypotenuse because it is the longest
[tex]\begin{gathered} (Hypotenuse)^2=4^2+2^2 \\ (Hypotenuse)^2\text{ = 16 + 4} \\ (Hypotenuse)^2\text{ = 20} \\ \text{ Take the squareroots of both sides} \\ \text{ }\sqrt[]{(Hypotenuse)^2\text{ }}\text{ = }\sqrt[]{20} \\ \text{Hypotenuse = }4.472 \\ \text{Hypotenuse }\approx\text{ 4.5} \end{gathered}[/tex]Hence, the length of the third leg is 4.5