Question

Use the formula for the total surface area of a cone to solve for the slant height l S=πrl+πr^2

Answer 1

s=
`\pi rl+ \pi r^(2)`
Making l the subject of the formula;
s-
`\pi r^(2) = \pi rl`
Dividing each side by
`\pi r`

`(s- \pi r^(2) )/( \pi r) =l`
L=
`(s- \pi r^(2) )/( \pi r)`