17.等腰三角形一腰上的高与另一腰的夹角为40°,则这个等腰三角形的一个底角的度数为( )
| A. | 50° | B. | 80° | C. | 50°或80° | D. | 25°或65° |
15.下列条件中,不能判定△ABC≌△DEF的是( )
| A. | ∠B=∠E,∠A=∠D,AC=DF | B. | BC=EF,∠C=∠F,AC=DF | ||
| C. | AB=DE,BC=EF,∠A=∠D | D. | ∠B=∠E,∠A=∠D,AB=DE |
13.
如图,已知在△ABC中,AB=AC,AB的垂直平分线DE交AC于点E,CE的垂直平分线正好经过点B,与AC相交于点F,求∠A的度数是( )
| A. | 30° | B. | 35° | C. | 45° | D. | 36° |
12.若m+$\frac{1}{m}$=$\sqrt{5}$,则m-$\frac{1}{m}$的值是( )
0 288761 288769 288775 288779 288785 288787 288791 288797 288799 288805 288811 288815 288817 288821 288827 288829 288835 288839 288841 288845 288847 288851 288853 288855 288856 288857 288859 288860 288861 288863 288865 288869 288871 288875 288877 288881 288887 288889 288895 288899 288901 288905 288911 288917 288919 288925 288929 288931 288937 288941 288947 288955 366461
| A. | ±2 | B. | ±1 | C. | 1 | D. | 2 |