The change in the $~y~$-coordinates when a plane is inclined, the coordinates are cartesian

Question

I have a plane of size wxh. Its a horizental plane (with $~x~$-axis the angle is zero).

I incline it with the angle alpha.

How would I calculate the $~y~$-coordinates?

I suppose that the $~y~$-coordinates remain the same.

Thanks

Shan