如图,在平面直角坐标系中,作出△ABC关于x轴对称的△A1B1C1,并写出C1点的坐标,并计算四边形ABC1C的面积.
解:△A1B1C1如图所示,点C1(-1,-1).四边形ABC1C的面积=18-1
The two cities have reached an _________ to develop science and technology.
Our English ______ far better in a month if we try harder.
下列材料最能证明“北京人已经会使用天然火”的是( )