Salut!
d=21 cm
At=400 cm²
d=L√3
L=d√3/3
L=7√3 cm
At= 2(L+l)+2(L+h)+2(l+h)
400 = 2(L+l)+2(L+h)+2(l+h)
200=L+l+L+h+l+h
2L+2l+2h=200
L+l+h=100 cm
Luam fata care are L si h
Diagonala unei fete: x
x=L√2
x=7√6 cm
Folosim teorema lui Pitagora pt a afla h
h²=L²+x²
h²=(7√3)²+(7√6)²
h²=49·3+49·6
h=√(49·9)
h=7·3
h=21 cm
l=100-L-h
l=100-7√3-21
l=79-7√3 cm
Succes!
