math.h中的常量

 #include<iostream>
 #include<iomanip>
  _USE_MATH_DEFINES
 #include<math.h>
     system(  a= cout<<setprecision( cout<<<<M_E<< cout<<<<M_LOG2E<< cout<<<<M_LOG10E<< cout<<<<M_LN2<< cout<<<<M_LN10<< cout<<<<M_PI<< cout<<<<M_1_PI<< cout<<<<M_2_PI<< cout<<<<M_PI_2<< cout<<<<M_PI_4<< cout<<<<M_SQRT2<< cout<<<<M_SQRT1_2<< cout<<<<M_2_SQRTPI<< cout<<<<oct<<a<< cout<<<<dec<<a<< cout<<<<hex<<a<< cout<<<<setbase()<<a<< cout<<<<setbase()<<a<< cout<<<<setbase()<<a<<   }