d1^2+d^2=a^2
d1+d2=b 2d1d2=S=b^2-a^2=21^2-15^2=6*36=216
сторона ромба = 40:4=10
d^2+3d^2=100
d=5
D=5sqrt(3)
S=2*25sqrt(3)=50sqrt(3)
d1^2+d^2=a^2
d1+d2=b 2d1d2=S=b^2-a^2=21^2-15^2=6*36=216
сторона ромба = 40:4=10
d^2+3d^2=100
d=5
D=5sqrt(3)
S=2*25sqrt(3)=50sqrt(3)