H=R*tg30^(o)=(2/7^(1/4))*(sqrt(3)/3)= [b]2sqrt(3)/(3*7^(1/4))[/b]
r=R/2=1/7^(1/4)
Тогда апофема боковой грани:
h^2=H^2+r^2=(2sqrt(3)/(3*7^(1/4)))^2+(1/7^(1/4))^2=
=((4/3)+1)/7^(1/2)
h=sqrt(7/3)/sqrt(7^(1/2)=7^(1/4)/sqrt(3)
a=R*sqrt(3)
S_(бок)=P_(осн)*h/2=3=(1/2)*3*R*sqrt(3)*(7^(1/4)/sqrt(3))=
=(3/2)*(2/7^(1/4))*(7^(1/4))= [b]3[/b]