Equilibrium of a stiff plate on inclined planes

[aang]

Well the first problem is α+β = 90.
IT is the exact same problem.
Do i really need to start a new thread for the same question.

 

[haruspex]

Well the first problem is α+β = 90.
IT is the exact same problem.
Do i really need to start a new thread for the same question.

and where α=45,β=60.

Those don't add to 90.
But more importantly, as with a new thread in a homework forum, you should show some attempt. A diagram employing the advances already made in this thread would be a good start.

Edit: aang has now started a new thread at https://www.physicsforums.com/threads/equilibrium-of-a-stiff-plate-on-inclined-planes.1004932/