Δ FCA drept
AC² = BC² + AB² =12² + 12² =144 + 144 = 144·2
AC= √144√2 = 12√2
AF² = CF² + AC² =12² + 144·2 = 144 + 144·2 =144·( 1 +2) = 144· 3
AF = √144√3 = 12√3
Δ EDA drept , notam DE =x
AE² = DE² + AD² = x² + 12² = x² + 144
daca Δ AEF isoscel , atunci AE=AF sau AE² = AF²
x² + 144 = 144 ·3
x² = 144· 3 - 144 = 144 · ( 3 - 1) = 144 · 2
DE = x = √144√2 =12√2
Spor !!!!!!
