mohon bantuannya.. pakein cara yg lengkap ya

[tex]\displaystyle D(x,y)=D\left(\frac{x_a+x_b+x_c}{3},\frac{y_a+y_b+y_c}{3}\right)\\D(x,y)=D\left(\frac{100+100+400}{3},\frac{500+200+200}{3}\right)\\D(x,y)=D\left(\frac{600}{3},\frac{900}{3}\right)\\D(x,y)=D(200,300)\\\\|AD|=\sqrt{(x_a-x_d)^2+(y_a-y_d)^2}\\|AD|=\sqrt{(100-200)^2+(500-300)^2}\\|AD|=\sqrt{100^2+200^2}\\|AD|=100\sqrt{5}\\\boxed{\boxed{|AD|=223,6\,\text{m}}}[/tex]