First of all, look at the derivation process of the arc length formula L =: Because the arc length corresponding to the central angle of 360 is the circumference c = 2π r (r is the radius of the circle), the arc length corresponding to the central angle 1 is 2πR/360, that is. The formula for calculating the arc length corresponding to the central angle n is L = n * 2π r/360l = n * π r/ 180 sector area: in a circle with radius r, since the sector area corresponding to the central angle 360 is the sector area S = π r 2, there is another sector area with the central angle N = NπR 2÷360. 2π=360 degrees. Because the unit of n is degree and l is angle. 0? 5= 1/2LR(n refers to the degree and l refers to the arc length) The lateral area of the cone is equal to the radius of the cone bottom multiplied by pi and then multiplied by the length of the bus.