The bottom surface of the pyramid p-abcd is a square with side length 1, and the side edge PA is perpendicular to the bottom surface ABCD. Moreover, PA = 2. If e is the midpoint of PA, we prove the plane BDE

The bottom surface of the pyramid p-abcd is a square with side length 1, and the side edge PA is perpendicular to the bottom surface ABCD. Moreover, PA = 2. If e is the midpoint of PA, we prove the plane BDE

If AC and BD are connected at point O, then:
OE//PC
And:
OE in plane BDE, PC out of plane BDE, and: PC / / OE
Then:
PC / / plane BDE