问题
选择题
命题p：∀x∈R，x2+1＞0，命题q：∃θ∈R，sin2θ+cos2θ=1.5，则下列命题中真命题是（ ）
A．p∧q
B．￢p∧q
C．￢p∨q
D．p∨q
答案
因为x2+1≥1＞0恒成立，命题p为真命题．
因为sin2θ+cos2θ=1，所以命题q为假命题．
所以p∧q为假命题，￢p∧q为假命题，￢p∨q为假命题，p∨q为真命题．
故选D．
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命题p：∀x∈R，x2+1＞0，命题q：∃θ∈R，sin2θ+cos2θ=1.5，则下列命题中真命题是（ ）
A．p∧q
B．￢p∧q
C．￢p∨q
D．p∨q
因为x2+1≥1＞0恒成立，命题p为真命题．
因为sin2θ+cos2θ=1，所以命题q为假命题．
所以p∧q为假命题，￢p∧q为假命题，￢p∨q为假命题，p∨q为真命题．
故选D．
| 选词填空。用方框中所给单词的适当形式填空，使短文通顺、正确、连贯（每个单词限用一次）。 | |
angry or afraid. Watch a dog 3____ , and you can find out how it feels. You can see what it is 4____ to tell you. When you are afraid, you may look down. When a dog is afraid, it may run away. When you are angry with other people, you stare at them and so 5____ an angry dog. Sometimes the hair along 6____ back stands up. Do you feel guilty when you have done something you shouldn't do? Dogs can feel guilty, too. At times when I come home, I'm 7____ a guilty look by my dog. Then I know he has done something wrong. Dogs need love and attention. Some dogs are very unhappy when they are left alone for a long time. Some dogs even snap 8____ they don't get enough attention. You may have a dog or you may know a dog. 9____ it well if you want to have fun with it. Play with it. Take it 10____ walks. Try not to punish it one time and not the next for doing the same thing. Always remember, a dog has needs and feelings just as you do. Talk to a dog, and it will talk to you . |