∴ quadrilateral ABGE is a parallelogram, ∴AE∥BG,
∠DGB is the angle formed by straight lines in different planes?
The side length of the cube is 1, DG = 52, BG = 52, DB = 2,
∴cos∠DGB= 15
The angle of a straight line on different planes is arccos 15. ..
(2) in: cubic ABCD-a1b1c1d1,∴BC⊥ surface EGC.
∴BC is the height of the triangular pyramid B-C 1CE,
∴VB 1？ C 1CE= 13？ SC 1CE？ BC = 13× 12× 1× 1× 1 = 16。