ExcelEnergyCorporation'snewonlinetrainingprogramhas_______(interact)featuresandforumdiscussionsfortrainees.
Anyvisitorstotheproductionfacilitiesmust____asecuritypassfromtheinformationdeskatthefrontentrance.
Hegavetheorderthatnothing_____untilthepolicearrived.
在三角形ABC中，AB=4，AC=6，BC=8，D为BC中点，则AD=（）
设三角区域D由直銭x+8y-56=0,x-6y+42=0与kx-y+8-6k=0(k<0)围成，则对任意的(x,y)，有㏒(x2+y2)≤2
(1)k∈(-∞,-1]
(2)k∈(-1,1/8]
