trapez isoscel B C
2
60⁰ A 1 E 2 F 1 D 60⁰
AB≡ CD ; CD = 2 cm
inaltimea BE in Δ AEB drept BE² = AB² - AE² =2² -1 = 3 ;BE=√3 cm
cos60⁰ = AE / AB ; 1 /2 = AE / 2 ; AE = 1 cm
daca AE =FD = 1 cm atunci EF = BC = 4 -1 -1 = 2 cm
aria = (4 + 2 )·√3 /2 = 6√3 /2 = 3√3 cm ²