The side area of the cone = the area of the sector isosceles triangle.

The waist length of this isosceles triangle = the generatrix length of the cone = the radius r of the sector.

The calculation of this area needs to know the included angle a of the sector.

Lateral area of s cone =0.5*(2R)sina/2*Rcosa.

The volume of the cone v = sh/3 = π r 2h/3.

π r 2 = the bottom area of the cone, and r is the diameter of the bottom of the cone.

2πr=πRa/ 180, which is the arc length corresponding to sector a.

Sector area = (π r 2) * (A/360)

This is the formula for all sectors and cones.

Just now, the area of the isosceles triangle was calculated with Rcosa/2, which is the height of the isosceles triangle inside the sector, and 2Rsina/2 is the chord length corresponding to the included angle A of the sector.