S=a*R^2/2
L= R*a
25pi=R*a
225pi=R^2a/2
450pi=R^2a
450pi/R^2=25pi/R
450pi/25pi=R
R=18
25pi= 18*a
a=25pi/18
a=250 град
S=a*R^2/2
L= R*a
25pi=R*a
225pi=R^2a/2
450pi=R^2a
25pi=R*a
450pi/R^2=25pi/R
450pi/25pi=R
R=18
25pi= 18*a
a=25pi/18
a=250 град