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dmmathwiz
Average Member

USA
7 Posts

 Posted - 09/06/2007 :  21:37:59 ....../\........(periods only used to keep spacing)...../..\c.........d/....\........./......\......./......./b...../_______/...........a.......... is where vector 'a' and 'b' meet. is where vector 'b' and 'c' meet.Find an equation relating the lengths, d,a,b,c, and the angles , and for figure above.Your expression should give d as a function of a, b, c, cos, cos, and cos(+).HINT: use the vector dot product and vector sum relation.I need help, i am assuming you set up an addition equation of the vectors to add up to d. Then i guess you need some how get it in the form of the stuff in the question.THANKS

dmmathwiz
Average Member

USA
7 Posts

 Posted - 09/08/2007 :  14:26:01 I came up with d * cos( + ) = a + bcos + ccosany ideas?

sahsjing

USA
2399 Posts

 Posted - 09/08/2007 :  19:06:39 quote:Originally posted by dmmathwiz....../\........(periods only used to keep spacing)...../..\c.........d/....\........./......\......./......./b...../_______/...........a.......... is where vector 'a' and 'b' meet. is where vector 'b' and 'c' meet.Find an equation relating the lengths, d,a,b,c, and the angles , and for figure above.Your expression should give d as a function of a, b, c, cos, cos, and cos(+).HINT: use the vector dot product and vector sum relation.I need help, i am assuming you set up an addition equation of the vectors to add up to d. Then i guess you need some how get it in the form of the stuff in the question.THANKSHint:Assume and are interior angles.a, b, c, d are all vectors.d = a + b + cx direction:dx = a - bcos() - ccos(+-)y direction:dy = bsin + csin(+-)d = (dx + dy) Edited by - sahsjing on 09/08/2007 20:28:44

dmmathwiz
Average Member

USA
7 Posts

 Posted - 09/10/2007 :  22:53:35 well thank you for all you help it was very helpful.my teacher said to take the approachd.d = (a+b+c) . (a+b+c)all letters are vectors, all "."'s are dot product.i ended up gettingd = a+b+c+2a.b+2a.c+2b.cwhich i then substituted in the definition of dot products.That is just the approach he wanted us to take, not sure how i would have come up with that, but i guess it works. Thanks Again.
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