Caranya seperti apa no 17f

AE/Sin C = EC/Sin A = AC/Sin D
ADC Siku siku di D
CD/Sin A=AC/Sin D
21/Sin 90°=AC/Sin 60°
21/1=AC/ 1/2akar3
AC=21.1/2akar3=21/2 akar3
AD=BC
AD=akar dr 21^2-(21/2 akar3)^2
=akar dr 441-441/4 .3
=akar dr (441.4 - 441.3) per 4
=akar dr 441/4
=21/2=10,5