# abs(x) is abolute value function; # abs(inverseabs(x_)):=x; # abs(zero) := zero; # abs(-zero) := -zero; # abs(x_,y_):=hypot(x,y)=sqrt(x^2+y^2); # abs(x_) := If(x>0, x, If(x<0,-x)); abs(a_*b_):= abs(a)*abs(b); abs(point(x_,y_)):=abs(x,y); abs(vector(x_,y_)):=abs(x,y); abs(vector(x_,y_,z_)):=abs(x,y,z);