View Compilation Error

0_0_25805038_25609.cpp: In function 'double calc1()':
0_0_25805038_25609.cpp:12:22: error: 'D' was not declared in this scope
  return 2.0*sqrt(R*R-D*D)/V;
                      ^
0_0_25805038_25609.cpp: In function 'double calc2()':
0_0_25805038_25609.cpp:16:24: error: 'D' was not declared in this scope
  return 2.0*sqrt(Rm*Rm-D*D)/V;
                        ^
0_0_25805038_25609.cpp: In function 'int main()':
0_0_25805038_25609.cpp:25:3: error: 'D' was not declared in this scope
   D=fabs(x*vy-y*vx)/V;
   ^