Draw a vertical line through the edge in the direction A, perpendicular to the foot B. ..

A is perpendicular to the other side, and the vertical foot is O.

Connecting BO, then ∠ ABO = 45 (∠ ABO is the plane angle of dihedral angle).

So, let PA=√2

In Rt△PAB, AB= 1,

In Rt△ABO, AO=√2/2. therefore

In Rt△APO, sin ∠ apo = ao/AP = (√ 2/2)/√ 2 =1/2.

∴∠APO=30，

That is, the angle formed by the straight line and the other plane of the dihedral angle is 30.