5.下列计算错误的是( )
| A. | 3$\sqrt{3}$-$\sqrt{3}$=2$\sqrt{3}$ | B. | a0=1 | C. | -2+|-2|=0 | D. | (-3)-2=$\frac{1}{9}$ |
20.
如图,AB是⊙O的直径,点C是⊙O上一点,∠BAC的平分线AD交⊙O于点D,过点D垂直于AC的直线交AC的延长线于点E.
(1)求证:DE是⊙O的切线;
(2)如果AD=5,AE=4,求⊙O的半径.
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(1)求证:DE是⊙O的切线;
(2)如果AD=5,AE=4,求⊙O的半径.