View Compilation Error

0_0_36454763_22648.cpp: In function 'int main()':
0_0_36454763_22648.cpp:49:42: error: 'circle' was not declared in this scope
         double ans = cl_inter(circle(R, a), circle(R, b)); //大圆交面积
                                          ^
0_0_36454763_22648.cpp:49:57: error: 'cl_inter' was not declared in this scope
         double ans = cl_inter(circle(R, a), circle(R, b)); //大圆交面积
                                                         ^