It is known that p-abc, PA ⊥ plane ABC, ab ⊥ AC, ab = AC = 4, AP = 5. (1) calculate the size of dihedral angle p-bc-a (the result is expressed by the value of anti trigonometric function). (2) rotate △ PAB (and its interior) around the line where PA is located to form a geometry, and calculate the volume V of the geometry

It is known that p-abc, PA ⊥ plane ABC, ab ⊥ AC, ab = AC = 4, AP = 5. (1) calculate the size of dihedral angle p-bc-a (the result is expressed by the value of anti trigonometric function). (2) rotate △ PAB (and its interior) around the line where PA is located to form a geometry, and calculate the volume V of the geometry

(1) In the isosceles triangle PBC and ABC, PD ⊥ BC, ad ⊥ BC, so ⊥ PDA is the plane angle of dihedral angle p-bc-a. & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; (2 points) in the isosceles right angle △ ABC, from ab = AC = 4 and ab ⊥ AC, ad = 22