Correct gesture for back swing is that the right upper arm's inside should be close to right armpit, while right elbow shapes an inverse triangle with unbend left arm.

正确的上挥杆姿势是右手上臂内侧应该紧贴右臂腋窝，右臂手肘与伸直的左臂呈一个倒三角形。然而一些球手在上杆的时候右臂向上抬起而并非紧贴身体。

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Coordination transform, triangle transform, etc are proposed to successfully derive the inverse kinematics analytic equations for the humanoid robot th 1 arms.

提出了坐标变换、三角变换等方法，巧妙求解出拟人机器人TH - 1手臂逆向运动学的解析表达式。

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