View Compilation Error

0_0_16392437_32667.cpp:12:5: error: stray '\' in program
     return 2.0*r*tan(pi\n);
     ^
0_0_16392437_32667.cpp: In function 'double getlen(int, double)':
0_0_16392437_32667.cpp:12:25: error: expected ')' before 'n'
     return 2.0*r*tan(pi\n);
                         ^