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Mathematics 18 Online
rvc (rvc):

vectors help please

rvc (rvc):

u ,v,w non-coplanar vectors then (u+v-w).[(u-v)x(v-w)]=

rvc (rvc):

A)0 B)u.(v x w) C)u.(w x v) D)3u.(v x w)

rvc (rvc):

@divu.mkr

OpenStudy (anonymous):

Just for the purpose of solving , assume u , v and w vectors as i+j , j , j+k ...I chose them because u-v=i and v-w=-k , so easy to plug values and get answer ..i got it as D..thinking of the proper method..

rvc (rvc):

nope the ans is B

rvc (rvc):

i want to know the working

OpenStudy (anonymous):

Yep , B ..i made a calculation error

rvc (rvc):

show me the working pls

OpenStudy (anonymous):

By this method of assuming values ? I am still thinking about the "proper" method

rvc (rvc):

yep i want to know @divu.mkr will tell me

OpenStudy (anonymous):

|dw:1426944476407:dw|

rvc (rvc):

okaay

rvc (rvc):

@divu.mkr start

OpenStudy (anonymous):

isnt it simple dot and cross??

rvc (rvc):

how to expand

rvc (rvc):

say

OpenStudy (anonymous):

normal expressions of dots and crosses.. cross --> uXv - uXw + vXw now take dot with every term outside just 3 terms will be there

OpenStudy (anonymous):

I thought it would be very lengthy to expand ! Turns out it wasn't lengthy at all ! :)

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