View Compilation Error

0_0_6764805_6498.c:7: error: syntax error before "acosl"
0_0_6764805_6498.c: In function `get_polar':
0_0_6764805_6498.c:64: error: `M_PI' undeclared (first use in this function)
0_0_6764805_6498.c:64: error: (Each undeclared identifier is reported only once
0_0_6764805_6498.c:64: error: for each function it appears in.)