Answer:
The right answer is the third option, 24,04 cm.
Step-by-step explanation:
Let's add an altitude FH.
Then, DH = HE = [tex]\frac{a}{2}[/tex] = 17.
[tex]FH^2=DH*HE \\ FH = \sqrt{17*17} \\ FH = 17[/tex]
FH = DH = HE = 17.
[tex]EF^2 = FH^2+HE^2\\ EF = \sqrt{289+289} \\ EF = \sqrt{578}[/tex]
[tex]\sqrt{578} = 24,0416... = 24,04.[/tex]
