How can I use a bempp operator's tangential as a new operator?

[zbl]

The integral equation I want to solve is:
lhs=0.5*Id+cross(n,E)
rhs=know

The “cross()” above means the vector’s cross product, and the vector ‘n’ is the unit normal vector upon the surface of the target. Moreover, the operater “Id” and “E” are the identity operator and boundary electric field operator, respectively. the “rhs” is kind of incient wave and it is known.

How can I express this cross(n,E) with Bempp?

I will very grateful for it if there is someone answer my question!

[zbl]

@zbl

e means the vector’s cross product, and the vector ‘n’ is the unit normal vector upon the surface of the target. Moreover, the operater “Id” and “E” are the identity operator and boundary electric field operator, respectively. the “rhs” is kind of incient wave and it is known.

How can I express this cross(n,E) with Bempp?

In other words, I need a tangential operator, to get the tangential of the boundary electric field operator.