Now a hot topic____(discuss) about whether the old computers in our school should be replaced____new ones. With the rapid____ ( develop) of science and technology, there is no doubt ____our old computers are totally out of date. The headmaster as well as the teachers and students____(be) not satisfied with the slow working speed of the computers. Therefore, all of them request to have a new computer so that their problems can be solved ____ （success).____the school should consider is ____to deal with the old computers wisely. Personally speaking,____(throw)  them away to the place____they are regarded as rubbish is not a good idea.

 过氧化钙晶体（CaO₂•8H₂O）较稳定，呈白色，微溶于水，广泛应用于环境杀菌、消毒．以贝壳为原料制备CaO₂流程如下：

某游乐场有两个长度相同的滑梯，要想使左边滑梯BC的高度AC与右边滑梯EF的水平方向的长度DF相等，则两个滑梯的倾斜角∠ABC与∠DFE的大小必须满足什么关系？说明理由．