A: You look very nice in your new dress today.B: Oh, really? I it when it was on sale.
A:buy
B:bought
C:have bought
D:will buy
在△ABC中,∠C=90°,若sinA=23,求cosB,tanB的值.
已知等比数列{an}中,a2=1,则其前3项的和S3的取值范围是( )
化学与生括、生产密切相关.请从①白醋 ②活性炭 ③熟石灰 ④小苏打中选择适当的物质填空(填序号)