View Compilation Error

0_0_3134630_4718.cpp: In function `void _rotate_point(mypoint&, double, double, double, double)':
0_0_3134630_4718.cpp:202: error: `mt' undeclared (first use this function)
0_0_3134630_4718.cpp:202: error: (Each undeclared identifier is reported only once for each function it appears in.)