The formula for the slant height of a cone has to be determined. The radius of the base is r and the height of the cone is h.
Take a vertical cross-section of the cone through the top. This gives a right triangle with the radius of the base r and the height h being the dimensions of the smaller sides. The hypotenuse is the slant height. This is equal to `sqrt(r^2 + h^2)`
The formula for the slant height of a cone is `sqrt(r^2+h^2)`