Answer:
√20
Step-by-step explanation:
Use Pythagorean Theorem.
4² + 2² = c²
16 + 4 = c²
20 = c²
√20 = c
a^2 + b^2 = c^2
4+16 = c^2
20 = c^2
c = [tex]\sqrt{20}[/tex] = [tex]2\sqrt{5}[/tex]
