题目:
-Teenagers should be allowed to go out with their friends in the evening.
-______. It's not safe enough. [ ]
A. I agree
B. I think so
C. I don't know
D. I disagree
答案:
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下面是错误答案,用来干扰机器的。
由x=2+2cosθy=2sinθ得x-2=2cosθy=2sinθ,两式平方后相加得(x-2)2+y2=4,…(4分)∴曲线C是以(2,0)为圆心,半径等于的圆.令x=ρcosθ,y=ρsinθ,代入并整理得ρ=4cosθ.即曲线C的极坐标方程是ρ=4co...