I got -5 for i but what do i do from there to solve ii (1 Viewer)

scaryshark09

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BA = -1i + 2j
BC = -1i - 3j

BA.BC = |BA||BC|cosABC

(-1)(-1) + (2)(-3) = (root5)(root10) cosABC

-5/root50 = cosABC

angle ABC = 135 degrees
 
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user18181818

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ohh i get it it's the same as what u did but just considering cos being negative
thanks
 

p711

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same thing as using AB.CB (the vectors should be both pointing to B or both away from B) im pre sure
 

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