Answer:
AC = 16
Step-by-step explanation:
In ΔABC & ΔABD
angle ABC = angle ADB ---- (each 90°)
angle BAD = angle CAB ---- (common)
so, therefore
ΔABC ~ ΔABD --- (by AA similarity)
by similarity in ΔABC & ΔABD
AB/AC = AD/AB
8/AC = 4/8
AC = 8×8÷4
AC = 16
