2.直线$\left\{{\begin{array}{l}{x=2+t}\\{y=\sqrt{3}t}\end{array}}\right.$(t为参数)被曲线x2-y2=1截得的弦长为( )
| A. | 2$\sqrt{10}$ | B. | $2\sqrt{7}$ | C. | $\sqrt{10}$ | D. | $\sqrt{7}$ |
1.曲线C的参数方程为$\left\{{\begin{array}{l}{x=sinα-cosα}\\{y=2sinαcosα}\end{array}}\right.(α为参数)$,则它的普通方程为( )
| A. | y=x2+1 | B. | y=-x2+1 | C. | $y=-{x^2}+1,x∈[{-\sqrt{2},\sqrt{2}}]$ | D. | y=x2+1,x∈[-$\sqrt{2}$,$\sqrt{2}$] |
20.在△ABC中,a=2$\sqrt{3}$,b=6,B=60°,则C等于( )
| A. | 30° | B. | 90° | C. | 150° | D. | 120° |
19.在Rt△ABC中,∠C=90°,a=1,b=3,则cosA=( )
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| A. | $\frac{3\sqrt{10}}{10}$ | B. | $\frac{\sqrt{10}}{10}$ | C. | $\frac{1}{3}$ | D. | 3 |