Question

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`

Answer 1

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)`