读壳体的零件图可以得到，该零件的高度尺寸基准为安装底板的下底面。http://image.zhihuishu.com/zhs/onlineexam/ueditor/201807/aeeb14bbf6ab4608b88e9eaf4baa4673.png

一简谐振动的旋转矢量图如右图，设图中圆的半径为R，则该简谐振动的振动方程为<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201807/dfd995a36f4e4dd2adb52a50cc5a26de.png"/> A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201807/e69d65d5dd4e49f9863425ce3fb5ac54.png"/> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201807/b13da9634fc9435398489686c8d362f9.png"/> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201807/e7906edc65b14dc39bafcb683986a690.png"/> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201807/0bfe1b068eac44d59d8772eb9bcbf871.png"/>

读拨叉零件图，完成下面的题目。 零件图用了（）个图形来表达形体结构。http://image.zhihuishu.com/zhs/onlineexam/ueditor/201806/9533fec959ab4ce98478025d0c3794f7.jpg

下图关于纯度对比9调图，5、6、3或7对比表述为（）http://image.zhihuishu.com/zhs/onlineexam/ueditor/201902/966c385068d44bcbb219377a417fd78b.png

http://image.zhihuishu.com/zhs/onlineexam/ueditor/201807/d95f303f761f4007a63f2df4a3f1596f.png