View Compilation Error

0_0_25076421_30273.cpp: In function 'int main()':
0_0_25076421_30273.cpp:11:3: error: 'Double' was not declared in this scope
   Double u_1 = atan(1.0/u);
   ^
0_0_25076421_30273.cpp:13:24: error: 'u_1' was not declared in this scope
   double v_1 = tan(s_1-u_1);
                        ^