19.若(m-n)(m-n-2)-8=0,则m-n的值为( )
| A. | 4或-2 | B. | 4 | C. | -2 | D. | 2 |
18.
如图,⊙O是△ABC的外接圆,直径AD=12,∠ABC=△DAC,则AC的长为( )
| A. | $6\sqrt{2}$ | B. | $6\sqrt{3}$ | C. | 8 | D. | 10 |
15.
如图,在Rt△ABC中,∠ACB=90°,AD平分∠BAC与BC相交于点D,若BD=4,CD=2,则AC的长是( )
| A. | 4 | B. | 3 | C. | 2$\sqrt{3}$ | D. | $\sqrt{3}$ |
11.
如图所示的长方形阴影区域的面积是( )
| A. | 9 | B. | 12 | C. | 14 | D. | 16 |
10.以下各图中,能确定∠1=∠2的是( )
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| A. | B. | C. | D. |