【单选题】已知直线l:xtanα-y-3tanβ=0的斜率为2,在y轴上的截距为1,则tan(a+β)=( )
【判断题】当合同中对某一问题未作出规定时,应参照有关国际贸易惯例。 ( )
【单选题】To assess how well a student is performing relative to his or her own previous performance,a teacher would use_________ assessment.
【简答题】已知直线 l : x tan a - y -3tan β =0的斜率为2,在 y 轴上的截距为1,则tan( α + β )=________.
【判断题】对于多元线性回归模型 ,参数β的最小二乘估计为 ,则 是β的无偏估计。
【简答题】在飞行中,由于 航线上各点的指向与经线的夹角始终保持不变,因而有利于用磁罗盘保持飞机的航向。
【单选题】What is the main idea of the second paragraph?
A.
Some plants have relative immunity to a great many diseases, while others have a susceptibility to them.
B.
The tolerance of a particular plant changes as the growing conditions change.
C.
A blight killed virtually every chestnut tree in North American.
D.
A blight may be a national infection.
【简答题】招标人和中标人应当在中标通知书发出( )13内,按照招标文件和中标人的投标文件订立书面合同。