请问这段英问的意思

请问这段英问的意思
HV plane calculation in relation to selected plane:
The normal of the working support is the same as the principal normal of the plane checked. You choose zx
plane, the PRINCIPAL NORMAL is Y
The first vector H is defined as follow : H= Z x N ( x means vectorial product). N is the normal vector y in our
case. H = -X.
The second vector V is defined as V = N x H. Don't forget that H;V;N must make a direct trihedron. Since V5 R7
you can reorient the axis system in the work support but the axis system must be direct. So changing one vector
H, change the other.

HV 平面与你所选择的平面相关：
工作支持面的法线方向与现在被点中平面的主法线方向一致。如果你选中zx平面，则主法线方向为y
第一个矢量H如此定义：H=ZxN(x为矢量乘积   注：遵循右手定则），在我们这个例子中N就是y，H=-X
第二个矢量V定义为V=NxH.但要记住:H,V,N构成三维直角坐标系。从V5 R7 开始你可以在工作支持面内重置坐标系，但是只限于直角坐标。所以当你改变H矢量时，另一个也要改变。