【单选题】The police think the fire was started ___________.
【简答题】设η是欧氏空间中一单位向量,定义T(α)=α-2(η,α)η.证明: (1)T是正交变换,这样的正交变换称为镜面反射; (2)T是第二类的(即T对应的矩阵的行列式为-1); (3)如果n维欧氏空间中,正交变换T以1作为一个特征值,且属于特征值1的特征子空间V1的维数是n-1,则T是镜面反射.
【单选题】下列哪组切牙舌面容易出现裂沟,好发龋坏?
【单选题】The film star claimed that the police action was a(n) _____ on her private life.
【简答题】Passage One Questions 46 to 50 are based on the following passage. Police officers may hope that their presence in schools will help them build strong relationships with students, improving police-com...