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Unununium111
New Member

USA
2 Posts

 Posted - 01/20/2011 :  23:36:45 Hey there, so it has been a while since I have taken Calc, and now I find myself in Calc 3 contemplating my career choices. Needless to say, I need some help proving a simple derivative of a vector-valued function, as I have never dealt with these. Of course I never have time to meet with the teacher when I work all day, so here I am. SO the problem states if |r(t)| > 0 , then show that:(d/dt)|r(t)| = {(1/|r(t)|)*r(t)} * {(d/dt)r(t)}What happens as |r(t)|=0 with {(d/dt)r(t)}?I have never seen a vector function until the other day, and I'm always uncomfortable with the 'prove this' type of general equations.Thanks in advance for the help!

royhaas
Moderator

USA
3059 Posts

 Posted - 01/21/2011 :  12:51:54 I believe your second "*" is actually a dot product. Write r(t)=x(t)i+y(t)j+z(t)k and use that.

maser22
New Member

USA
2 Posts

 Posted - 04/05/2011 :  11:36:55 Hi,I wanted to let you know about a superb mathematician who works as a tutor for a homework help website.If you want to consult with her on any math issues, click on the link and submit a Solution Request. Your request will go to her directly if you enter "rlehman" in the Specialist's username field during your submission. You won't be sorry, as she is the real deal.Please post back to me here and let me know what you think of her.
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