Hi BSD,
The question is ill-posed in the sense , that you will be able to see just a line in the Y-Z plane as the triangle lies in the x-y plane. When you rotate to the Y-Z plane, you discard the variations of the X -plane completely. In other words you discard the evolution of the triangle in the x-y plane. Think of it like this, If you place a bottle on your table and watch it sitting on your chair in front of it then you are watching it in one perspective and orientation. Now if you stand up and watch it from above you will get a different view. The view you get of an object is essentially characteristic of the plane in which you are viewing them and hence in this sense, you cannot see the triangle in the same form as it is in the x-y plane. Hope this assists.
Happy to Help
UJJWAL
