Explicație pas cu pas:
CN _|_ AB
CN = AD = 6 cm
[tex]CN² = AN × NB => NB = \frac{ {6}^{2} }{18} = 2cm\\AB = AN + NB = 18 + 2=20 \: cm[/tex]
[tex]AC = \sqrt{2 \times 20} = 2 \sqrt{10} \: cm[/tex]
[tex]perimetrul = 20 + 2 \sqrt{10} + 18 + 6 = 44 + 2 \sqrt{10} = 2(22 + \sqrt{10} ) \: cm[/tex]\\