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【单选题】
在采用步进电动机与滚珠丝杠直接传动的数控铣床工作台中,滚珠丝杠的基本导6mm,步进电动机的歩距角为1.5°,其脉冲当量为( )。A.
0.025mm
B.
0.05mm
C.
0.0125mm
D.
0.01mm
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举一反三
【单选题】设函数y=f(-x 2 )，则dy等于( )
A.
xf'(-x 2 )dx
B.
-2xf'(-x 2 )dx
C.
2f(-x 2 )dx
D.
2xf'(-x 2 )dx
【简答题】求势函数u(x，y)，使得 (1)du=(3x 2 -3y 2 +4)dx-6xydy (2)du=(e x siny+2xy 2 )dx+(e x cosy+2x 2 y)dy.
【简答题】Passage One Questions 56 to 60 are based on the following passage. Last week I visited one of my old neighborhoods in Washington D.C. I had not been there for twenty years and as I walked along the st...
【简答题】Questions 24 -27 are based on the following passage. Living in the city is hard. I was born and raised in Dallas, so l know first-hand about heavytraffic and busy roads. However, when I moved to New Y...
【简答题】Passage Two Questions 1 to 5 are based on the following passage. Forgiving is easy. Forgetting the experience that comes before the forgiveness, however, always remains with us. Choosing to forgive me...
【简答题】2xydy=(2y 2 -x)dx．
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