You'll see why very soon, in such a way that the derivative is this given unit vector u hat.

你很快就会明白为什么,导数dr/ds等于给定的单位u向量。

youdao

Park shot to stardom after scoring a hat-trick to help unfancied South Korea to a convincing 3-0 win against host China in the 2004 AFC U-19 Women's Championship final.

在2004年举行的女足亚青赛上，朴恩善的帽子戏法帮助名不见经传的韩国队3比0大胜东道主中国队，一战成名。

youdao

Plus the U. S. and Israel are close Allies so visiting that country reinforces this strength of hat relationship.

加上美国和以色列是亲密盟友，因此访问那个国家加强这种关系。

youdao

Within five minutes of the restart, Sa'u had his hat-trick - first, finishing off another fluid movement in the corner and then dancing through the tackles to race over as New Zealand again took advantage of the opposition's short condensed line.

BBC: New Zealand 76-12 Papua New Guinea

Although the Obama administration "won't be passing the hat, " U.S. officials expect that some NATO countries will announce in Chicago commitments to pay for the Afghan army and police post-2014.

CNN: G8 and NATO-athon, with Pakistan at the table

But three-quarters Junior Sa'u and Sam Perrett both completed hat-tricks as the home side took their try tally to 14 and moved a step nearer the final.

BBC: New Zealand 76-12 Papua New Guinea