2.已知函数$f(x)=\left\{{\begin{array}{l}{cosx-1,x≤0}\\{{{sin}^2}x,x>0}\end{array}}\right.$,则下列结论正确的是( )
| A. | f(x)是偶函数 | B. | f(x)是单调函数 | C. | f(x)是周期函数 | D. | f(x)的值域为[-2,1] |
1.已知直线ax-by+2=0与曲线y=x3-1在点P(1,0)处的切线垂直,则$\frac{a}{b}$=( )
| A. | $\frac{1}{3}$ | B. | $-\frac{1}{3}$ | C. | $\frac{2}{3}$ | D. | $-\frac{2}{3}$ |
18.已知直线bx+ay+2=0与曲线y=x3-1在点P(1,0)处的切线平行,则$\frac{a}{b}$=( )
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| A. | $\frac{1}{3}$ | B. | $-\frac{1}{3}$ | C. | $\frac{2}{3}$ | D. | $-\frac{2}{3}$ |