等边平行四边形铰链机构
Hinge Unit of Equilateral Parallelogram
补充平行四边形
supplementary parallelogram
基本周期平行四边形
fundamental period parallellogram
fundamental period-parallelogram
fundamental period parallelogram
力平行四边形定律
principle of the parallelogram of forces
平行四边形单元
four nodded parallelogram element
平行四边形的对角线
diagonal of a parallelogram