Dear all

I am using Physics[Vectors] package of Maple 17. I want to define an orthogonal curvilinear coordinates through alpha and beta independent variables. To define unit vectors of alpha and beta, I have to apply the derivatives of position vector r_ with respect to alpha and beta, respectively. Please help me to define the unit vectors in directions alpha and beta as derivatives of position vector r_ with respect to alpha and beta, respectively. Please see the below Code:

**> restart;**

**> with(Physics[Vectors]);**

**> Setup(mathematicalnotation=true);**

**> r_:=X(alpha,beta)*_i+Y(alpha,beta)*_j+Z(alpha,beta)*_k;**

The unit vectors in directions alpha and beta should be defined as:

_alpha=diff(r_,alpha)

_beta=diff(r_,beta)

It is worthwhile to mention that the following expression governs:

**> diff(r_,alpha).diff(r_,beta)=0;**

Please guide me.

Best wishes

Ali