Resposta :
a² = b² + c²
5² = 4² + c²
25 = 16 + c²
25 - 16 = c²
9 = c²
c = √9
c = 3cm
[tex]\large\boxed{\begin{array}{l} \rm \: 5 {}^{2} = 4 {}^{2} + c {}^{2} \\ \rm \:25 = 16 + c {}^{2} \\ \rm \: 25 - 16 = c {}^{2} \\ \rm \: 9 \: = \: c {}^{2} \\ \rm \: c {}^{2} = 9 \\ \rm \: c = \sqrt{9} \\ \boxed{ \rm{c = 3 \: cm}} \end{array}}[/tex]