As shown in the figure, PA ⊸ o is in the plane, AB is the diameter of ⊙ o, C is the point on ⊙ o, and E.F is the point a in the plane PB.PC The following conclusions are given: 1, AF ⊥ Pb; 2, EF ⊥ Pb; 3, AF ⊥ BC; 4, AE ⊥ plane PBC, where the sequence number of the correct proposition is

As shown in the figure, PA ⊸ o is in the plane, AB is the diameter of ⊙ o, C is the point on ⊙ o, and E.F is the point a in the plane PB.PC The following conclusions are given: 1, AF ⊥ Pb; 2, EF ⊥ Pb; 3, AF ⊥ BC; 4, AE ⊥ plane PBC, where the sequence number of the correct proposition is

To be brief
AB is diameter → AC ⊥ BC
PA ⊥ plane ABC → BC ⊥ pa
Above two → BC ⊥ plane PAC → BC ⊥ AF
So conclusion 3 is correct
BC ⊥ AF and PC ⊥ AF → AF ⊥ plane PBC → AF ⊥ PB
Conclusion 1 is correct
AF ⊥ Pb and AE ⊥ Pb → Pb ⊥ plane AEF → EF ⊥ PB
Conclusion 2 is correct
Conclusion 4 is wrong because two perpendicular lines can not be drawn from one point to one plane
The above push out symbols are all replaced by →, because the push out symbol can not be typed ==

The length of the oblique line PA passing through a point p outside plane a is 3 / 3 times of the length of the vertical line Pb passing through this point (a, B belong to a)
Don't copy it online
It's better to have a picture,
The answer is 60 degrees, today!

Hello
PA=2√3/3PB
sina=PB/PA=3/（2√3）=（√3）/2
a=60º

The vertical line Po and two oblique lines PA and Pb are drawn from a point p outside plane a to plane A. their projective lengths in plane a are 2cm and 12cm, and the two oblique lines are parallel to plane a
The angle difference is 45 degrees, and the length of Ao is calculated

Let the length of Ao be X. from the meaning of the question, we can get: arctg (x / 12) + pi / 4 = arctg (x / 2)
The solution is: x = 4,6

From a point P out of the plane, we can find the degree of the angle between the oblique line PA and plane a by introducing the vertical line Po and oblique line PA of plane a, Po = 3, PA = 6

Connecting OA, the angle Pao is the angle formed by the straight line PA and plane a, which is set as θ
Because Po = 3, PA = 6
sinθ=3/6=1/2
So theta = 30 degrees