Making paper cones

Excel formula for finding concentric frustum of cone.

Where:
r is inner radius, e.g. 2.50
R is outer radius, e.g. 4.00
h is height of frustum, e.g. 4.00

r1 = SQRT((h*r/(R-r))^2+r^2), e.g. 7.120003
r2 = r1*R/r, e.g. 11.392
Angle = r/r1*360degrees, e.g. 126.4044

To make a rolled paper frustum of a cone, use 7.12 as the inner radius, 11.39 as the outer radius and cut at angle of 126.4 degrees.