The radius of the base of a right circular cone of semi-vertical angle `alpha` is `r` . Show that its volume is `1/3pir^3` `cotalpha` and curved surface area is `pir^2` `cos e s` `alphadot`

Explanation

Volume of cone=`1/3pir^2h`

`tan(alpha)= r/h`

`h=rcot(alpha)`

Volume of cone=` 1/3pir^3cot(alpha)`

curved surface area= `pirl`
`sin(alpha) = r/l`
`curved surface area= pir^2cosec(alpha)`