/in/foo.cc: In function 'int main()':
/in/foo.cc:17:12: warning: unused variable 'x3' [-Wunused-variable]
   17 |     double x3=x1-x4*cos72+y4*sin72;
      |            ^~
/in/foo.cc:18:12: warning: unused variable 'y3' [-Wunused-variable]
   18 |     double y3=y1-x4*sin72-y4*cos72;
      |            ^~