4.
如图,在△ABC中,∠C=90°,AB=5,AC=4,则sinA的值是( )
| A. | $\frac{3}{4}$ | B. | $\frac{5}{3}$ | C. | $\frac{4}{5}$ | D. | $\frac{3}{5}$ |
2.下列运算中,结果是a6的是( )
| A. | a3•a2 | B. | (a3)3 | C. | a3+a3 | D. | (-a)6 |
20.
如图,直线y=$\frac{3}{4}x+3$与x、y轴分别交于A、B两点,则cos∠BAO的值是( )
| A. | $\frac{4}{5}$ | B. | $\frac{3}{5}$ | C. | $\frac{4}{3}$ | D. | $\frac{5}{4}$ |
19.下列运算正确的是( )
0 282945 282953 282959 282963 282969 282971 282975 282981 282983 282989 282995 282999 283001 283005 283011 283013 283019 283023 283025 283029 283031 283035 283037 283039 283040 283041 283043 283044 283045 283047 283049 283053 283055 283059 283061 283065 283071 283073 283079 283083 283085 283089 283095 283101 283103 283109 283113 283115 283121 283125 283131 283139 366461
| A. | a2×a3=a6 | B. | a2+a2=2a4 | C. | a8÷a4=a4 | D. | (a2)3=a5 |