5.
12 cm : 3 części = 4 cm
|CD| = 4 cm
|CF| = 6 cm
|CD|² + |CF|² = |FD|²
4² + 6² = |FD|²
4 · 4 + 6 · 6 = |FD|²
16 + 36 = |FD|²
|FD|² = 16 + 36
|FD|² = 52
|FD| = √52
Odp: A