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anonymous
 4 years ago
Find II 2e3f II assuming that e & f are unit vectors such that II e +f II=sqrt(3/2).I tried using the law of cosines but not getting it...
anonymous
 4 years ago
Find II 2e3f II assuming that e & f are unit vectors such that II e +f II=sqrt(3/2).I tried using the law of cosines but not getting it...

This Question is Closed

beginnersmind
 4 years ago
Best ResponseYou've already chosen the best response.1Draw e+f, and solve for the angle.

beginnersmind
 4 years ago
Best ResponseYou've already chosen the best response.1Do you need another hint?

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0not yet, doing math & watching my 3year old and 1 year old sister is interesting...makes solving problems kind of slow...i'll post if i need another hint thanks!

beginnersmind
 4 years ago
Best ResponseYou've already chosen the best response.1Ok, sometimes people get stuck but don't speak up until you ask :(

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0why am I finding the theta between e & e+f....theta=e dot e+f / sqrt(3/2)...

beginnersmind
 4 years ago
Best ResponseYou've already chosen the best response.1You need theta between e and f.dw:1335665267401:dw

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0but then theta=e dot f what is that...

beginnersmind
 4 years ago
Best ResponseYou've already chosen the best response.1Where is e+f on the picture? You have a triangle and you know the length of all 3 sides.

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0dw:1335665495008:dw

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0got it got it got it....

beginnersmind
 4 years ago
Best ResponseYou've already chosen the best response.1ok, that saves me some drawing :)

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0now i can move on lol i hope that you aren't much younger than me, i'm very competitive but i gotta hand it to you! idk why I got stumped i tutor calc 3!!! >:/

beginnersmind
 4 years ago
Best ResponseYou've already chosen the best response.1I'm probably not :)

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0\[ (e+f) . (e+f)=e.e + e.f + f.e + f.f=2 +2 e.f= \frac 32\\ e.f =\frac 1 4\\ (2e 3f).(2e3f)=4e.e  6 e.f 6 f.e +9f.f =\\ 13  12 e.f= 13 + 3=16\\  2e  3f =\sqrt{(2e 3f).(2e3f)} =\sqrt {16}=4 \] where u.v is the dot product of u and v

beginnersmind
 4 years ago
Best ResponseYou've already chosen the best response.1Wow, that's actually nicer than calculating the angle between e and f and writing them in a new coordinate system.

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0Actually for any m and n  m e  n f can be calculated and depends only on m and n and e.f
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