{$A+,B-,D+,E+,F-,G-,I+,L+,N+,O-,P-,Q-,R-,S+,T-,V+,X+,Y+}
{$M 16384,0,655360}
const
pi=3.1415926535;
g=10.00;
var
i,j,k,n:longint;
v,a,m,b,ans:extended;
begin
  assign(input,'e:\ru.in');
  reset(input);
  readln(v,a,m);
  b:=2*sin(a/180*pi)*cos(a/180*pi)/g;
  ans:=b*v*v/(1-1/m);
  writeln(ans:0:2);
end.

You could get more convenient formula for the answer.
v^2/10*k/(k-1)*sin((pi*a)/90)

Could you or somebody else explain the formula?

look on sum of an infinitely decreasing geometric progression
where k=1/q
i hope you will understand

sin(alpha) * cos(alpha) = sin(2 * alpha) / 2