垂直一定相交,相交一定垂直.______.
由分析可知:垂直一定相交,但相交不一定垂直,故本题说法错误;
故答案为:错误.
已知▱ABCD的两条对角线AC、BD相交于点O,如果△AOB的面积是3cm2,那么▱ABCD的面积是______cm2.
Frame Relay is simplified form of (71) ,similar in principle to (72) , in which synchronous, frames of data are routed to different destinations depending on header information. Packets are routed throught one or more Virtual Circuits known as (73) . Most Virtual Circuits are (74) ,which means that the network provider sets up all DLCI connections at subscription time. (75) are also part of the Frame Relay specification. They privide a link that only lasts only as long as the session.
A.Permanent Circuits
B.Permanent Virtual Circuits
C.Switched Virtual Circuits
D.Switching Circuits