挑战习题
1/5单选题
难度:

1.边长为1的正方形OABC的顶点A在x正半轴上,点C在y正半轴上,将正方形OABC绕顶点O顺时针旋转75°,如图所示,使点B恰好落在函数y=ax2(a<0)的图象上,则a的值为(  )
A
B 1
C
D
提示1:
IOi/h+eCuULlkJF46L205byV5Z6C57q/77yM6L+e5o6lT0LvvIzlj6/lvpdPQueahOmVv+W6pu+8jOi/m+iAjOW+l+WIsOeCuULnmoTlnZDmoIfvvIzku6PlhaXkuozmrKHlh73mlbDop6PmnpDlvI/ljbPlj6/msYLop6M=
正确答案:RA==
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