① <img class=jc-formula data-tex={ x }_{ i } src=https://huaweicloudobs.ahjxjy.cn/DF5736EE37FCDDF2830385E536CC66D1.png style=vertical-align: middle;/>
② <img class=jc-formula data-tex={ x }_{ j } src=https://huaweicloudobs.ahjxjy.cn/62C3385988FD7A88E1F56176D8EDCC1F.png style=vertical-align: middle;/>
③ <img class=jc-formula data-tex={ x }_{ i } src=https://huaweicloudobs.ahjxjy.cn/DF5736EE37FCDDF2830385E536CC66D1.png style=vertical-align: middle;/>方向的位移