ok so what is do is
the bottom half is the radius
the top half is a little bit m ore tricky
we can do
18=base
15=sides
makes an equilateral traignel
split it up into
base 18/2=9
hypotonuse 15
height=?
9^2+x^2=15^2
81+x^2=225
x^2=144
x=12
height=12
add
radis=15
height=12
15+12=27
27 cm
