【多选题】专业店和专卖店经营特点的不同之处在于 ( )
【简答题】(文科)设向量 =(cos23°,cos67°), =(cos68°,cos22°), = +t (t∈R),则| |的最小值是____________ (理科)已知a>0,设函数f(x)= +sinx,x∈[-a,a]的最大值 为M,最小值为m,则M+m=__________
【简答题】向量 a =(cos23°,cos67°), b =(cos68°,cos22°), u = a +t b (t∈R). (1)求 a ? b ; (2)求 u 的模的最小值.
【简答题】The Voice of America began during the WorldWar II . When Germany was broadcasting a radio program to get international ___1___ , American officials believed they should ___2___ the German broadcast wi...
【简答题】(文科)设向量 a =(cos23°,cos67°), b =(cos68°,cos22°), u = a +t b (t∈R),则| u |的最小值是______.
【单选题】计算cos23°sin53°-sin23°cos53°的值等于( )