InterviewSolution
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InterviewSolution
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`A B C D E`is pentagon,prove that` vec A B`+ ` vec B C`+ ` vec C D`+ ` vec D E+ vec E A`= ` vec0`` vec A B+ vec A E+ vec B C+ vec D C+ vec E D+ vec A C=3 vec A C` |
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Answer» `vecR=vec(AB)+vec(AE)+vec(BC)+vec(DC)+vec(ED)+vec(AC)` `" "=(vec(AB)+vec(B C))+(vec(AE)+vec(ED)+vec(DC))+vec(AC)` `" "=vec(AC)+vec(AC)+vec(AC)=3vec(AC)` |
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