Explicație pas cu pas:
AP ≡ RC = 360 m
AR ≡ PC = 800 m
PB = 480 m =>
BC = PC - PB = 800 - 480 = 320
=> BC = 320 m
DR = 120 m =>
CD = CR - DR = 360 - 120 = 240
=> CD = 240 m
ΔAPB: AB² = AP² + PB² = 360² + 480²
=> AB = 600 m
ΔBCD: BD² = BC² + CD² = 320² + 240²
=> BD = 400 m
ΔARD: AD² = AR² + DR² = 800² + 120²
=> AD = 40√409 m
[tex]Perimeter_{\triangle ABD} = AB + BD + AD \\ = 600 + 400 + 40√409 = 40(25 + √409) m[/tex]
√409 ≈ 20,22
[tex]\implies P_{\triangle ABD} = 40(25 + √409) \: m \\ ≈ 1809 \: m > 1800 \: m = 1,8 \: km \\ [/tex]
