[library]: fix bug for M_PI
[library]: fix bug for M_PI

li12242/NDGFEM_Matlab,li12242/NDG-FEM,li12242/NDG-FEM,li12242/NDG-FEM,li12242/NDGFEM_Matlab,li12242/NDGFEM_Matlab,li12242/NDGFEM_Matlab,li12242/NDG-FEM