limas beraturan

AB = AD = 4 cm

AT = 5 cm

O tengah ABCD

TO tinggi limas

AC = 4√2 cm

AO = 1/2 AC = 2√2 cm

TO = √(AT² – AO²)

TO = √(5² – (2√2)²)

TO = √17 cm

perhatikan segitiga BDT

X pada TB

DX ⊥ TB

Jarak D ke TB

= DX

= DB × TO / TB

= 4√2 × √17 / 5

= 4/5 √34 cm