Glossary of angles in solid geometry

In a 3D Euclidean space, there is a tetrahedron $V-ABC$ where $\triangle ABC$ is equilateral and $VA=VB=VC$ , $P$ is a point on edge $VA$ (not including point $V$ and $A$ ).

Angle $\alpha$ denotes the acute angle of the line $PB$ and $AC$ , $\beta$ denotes the angle of $PB$ and plane $ABC$ , and $\gamma$ denotes the dihedral angle $P-AC-B$ .

Which of the following is true ?

Show your rigorous proof.