View Compilation Error

0_0_11860074_20078.cpp:2: error: `usingnamespace' does not name a type
0_0_11860074_20078.cpp: In function `double fun(double)':
0_0_11860074_20078.cpp:6: error: `return1' undeclared (first use this function)
0_0_11860074_20078.cpp:6: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_11860074_20078.cpp:6: error: expected `;' before numeric constant
0_0_11860074_20078.cpp: In function `int main()':
0_0_11860074_20078.cpp:27: error: `return0' undeclared (first use this function)