It is calculated that SA = 23, so V = 13× SABCD× SA = 23.
(2) Connect alternating current. Since EF and 12AC are parallel and equal, ∠ACD is the angle formed by the straight line EF and CD.
It is calculated that AC=22, CD=5, 1=8+5-4 10cos∠ACD, cos ∠ ACD = 310/kloc-0,
TherEFore, the off-plane straight line ef forms an angle of arccos3 10 10 with CD.