View Compilation Error

0_0_20479232_18329.cpp: In function 'double find_r(double, double, double, double, double, double)':
0_0_20479232_18329.cpp:27:55: error: invalid type argument of unary '*' (have 'double')
     s = fabs( * ((x1-x3) * (y2-y3) - (x2-x3) * (y1-y3)));
                                                       ^