Question 1022027
The base circumference will be missing from the unfolded circular surface.  The radius of this unfolded circle will be same as slant height of the cone.


{{{L=sqrt((24/2)^2+5^2)}}}
{{{L=sqrt(144+25)}}}
{{{L=sqrt(169)}}}
{{{highlight(L=13)}}}---------radius of this sector


If this unfolded part were a full circle, circumference would be {{{2*pi*13=highlight(26pi)}}}; 


The circumference of the base:  {{{2*pi*(24/2)=24pi}}};
Angle of this sector is  {{{360((26-24)/25)=360(2/25)=144/5=highlight(28.8*degrees)}}}.