The arc length of the sector = the degree of the central angle of the arc *2* the circular radius of the arc, that is, l =(n*2* pie (3. 14)*R).

Sector area = degree of central angle of arc * square of circular radius of arc, that is, S sector = (n * pie (3.14) * r * r.

Area of the sector = 1/2* arc length of the sector * radius of the circle opposite to the arc, that is, S sector = (1/2) * l * r.

Expand the cone into a fan shape, that is, the generatrix = the radius of the circle subtended by the arc, and the side length of the cone s = (1/2) * l * r.

The arc length of the conical fan is the circumference of the lower half circle.

So l=2* pie *r

S- cone edge = (1/2) * r * 2 * pie * r = pie * r * r.

Note: l= sector arc length =2* pie *r

Pie =3. 14 R= radius of arc to circle = bus.

R= radius of the bottom semicircle