更新1:
http://www.flickr.com/photos/11667399@N03/5369783017/
更新2:
有條問題,不過我真係好想搞清個CONCEPT..唔係只係知道個ANS~
更新3:
仲係唔係好明 1."This is equal to the normal vector at the point,normal in a sense that it is normal to the countour of equal concentration." 2."This vector is also the path of maximum rate of change ,so it is atangent of the shark's path." 係咪有得PROOF,,可唔可以PROOF 埋比我睇,THX
更新4:
equal係咪指佢地個value??
更新5:
1. 佢地唔係prependicular to each other 咩??
