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网格是一个简单又特殊的领域,将简单的图形放入网格,可以展示出许多奇妙的变换,下面就让我们一起来欣赏网格中的旋转问题.一、求旋转角例1如图1,点A、B、C、D、O都在方格纸的格点上,若△COD是由△AOB绕点O按逆时针方向旋转而得,则旋转的角度为().A.30°B.45°C.90°D.135°解析:首先要确定一组对应边,然后求出它们的夹角,它们的夹角就是旋转的角.观察图形可知OB就是OD绕点O按逆时针方向旋转而得,这时旋转了90°,故选C.点评:旋转角是一对对应点与
Grid is a simple and special field, the simple graphics into the grid, you can display many wonderful transformations, let us appreciate the rotation of the grid together below. 1, point A, B, C, D, O are in grid cell grid point, if △ COD is △ AOB around point O counterclockwise rotation, the angle of rotation is () .A. 30 ° B.45 ° C.90 ° D.135 ° Resolution: First of all, to determine a set of corresponding edges, and then find their angle, their angle is the angle of rotation.Observe the graphics OB is OD around the point O By rotating counterclockwise derived, then rotated 90 °, so choose C. Comments: rotation angle is a pair of corresponding points and