View Compilation Error

0_0_37553792_32356.cpp: In function 'int main()':
0_0_37553792_32356.cpp:18:50: error: 'b' cannot be used as a function
   ans=a*b(3.1415/4-xb/(a*2)*(yb/b+1/2*asin(xb/a)))+(y*xb*xb)/(2*x);
                                                  ^