4.已知点A(6,4),B(6,-6),则点A与点B的关系是 ( )
| A. | 关于x轴对称 | B. | 关于y轴对称 | ||
| C. | 关于直线y=-1对称 | D. | 关于直线x=-1对称 |
18.
如图,在△ABC中,∠C=90°,点0为△ABC的三条角平分线的交点,0D⊥BC,0E⊥AC,0F⊥AB,点D、E、F分别是垂足,且AB=5cm、BC=4cm,CA=3cm,则点0到三边AB、AC和BC的距离分别等于 ( )
0 309835 309843 309849 309853 309859 309861 309865 309871 309873 309879 309885 309889 309891 309895 309901 309903 309909 309913 309915 309919 309921 309925 309927 309929 309930 309931 309933 309934 309935 309937 309939 309943 309945 309949 309951 309955 309961 309963 309969 309973 309975 309979 309985 309991 309993 309999 310003 310005 310011 310015 310021 310029 366461
| A. | 1cm,1cm,1cm | B. | 1.5cm,1.5cm,1.5cm | ||
| C. | 2cm,2cm,2cm | D. | 2cm,1.5cm,1cm |