July 14th, 2015, 01:13 PM  #1 
Member Joined: Sep 2013 Posts: 58 Thanks: 0  Gradient Question
So I don't get what I did wrong either. fx(1.3)=6x=6(1)=6 fy(1,3)=6y=6(3)=18 Gradiant <6,18> Length is Sqrt((6)^2+(1^2)=Sqrt(360). Unit Vector =1/sqrt(360)<6,18> b) I'm not sure if we find the Length of the Gradiant Vector of length of the Unit Gradiant Vector Gradiant <6,18> Length of Gradiant: Sqrt(360) What am I doing wrong?  
July 14th, 2015, 02:18 PM  #2 
Member Joined: Sep 2013 Posts: 58 Thanks: 0 
Nevermind. The question asks for the fastest descent (slope is negative), while the gradient always gives the fastest ascent (where the slope is positive. I needed to multiple the vector<6,8> by negative one to get to a unit vector of 1/sqrt(360)<6,18> and hence a fastest downward speed of sqrt(360). Sorry for the trouble. You can close the thread. From, Tzad 

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