超重机的底座、输电线路的支架、自行车的斜支架等,都是采用三角形结构,这样做的数学道理是利用了____ .
设a=logπ3,b=log34,c=log417,则( )
— ________ do you go to school?
—I often go to school ________ 7:30 am.
69+6=____