tolong bantu yang nomor 8 saja pake cara

Semoga jelas ya jawabannya :)

BD = 4 cm
AD = 8 cm
CD = 16 cm

a)
AC^2 = CD^2 + AD^2
AC^2 = 16^2 + 8^2
AC^2 = 256 + 64
AC^2 = 320
AC = V320
AC = V(64 × 5)
AC = 8V5 cm

b)
AB^2 = BD^2 + AD^2
AB^2 = 4^2 + 8^2
AB^2 = 16 + 64
AB^2 = 80
AB = V80
AB = V(16 × 5)
AB = 4V5 cm

c)
ya karena :
AC^2 + AB^2 = BC^2
(8V5)^2 + (4V5)^2 = (16 + 4)^2
320 + 80 = 20^2
400 = 400 (terbukti siku-siku)