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Let `vecA , vecB and vecC` be vectors of legth , 3,4and 5 respectively. Let `vecA` be perpendicular to `vecB + vecC, vecB " to " vecC + vecA and vecC " to" vecA + vecB` then the length of vector `vecA + vecB+ vecC` is __________. |
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Answer» Correct Answer - `5sqrt2` Given that `|vecA|=3, |vecB|=4, |vecC|=5` `vecAbot (vecB + vecC) Rightarrow vecA. (vecB +vecC) =0` `Rightarrow vecA.vecB + vecA.vecC=0` ` vecB bot (vecC +vecA)RightarrowvecB.(vecC+vecA_=0` `Rightarrow vecB.vecC+vecB.vecA=0` `vecCbot (vecA+vecB) RightarrowvecC. (vecA+vecB)=0` ` Rightarrow vecC.vecA+vecC.vecdB=0` Adding (i), (ii) and (iii) we get `2(vecA.vecBr+vecB.vecC+vecC.vecA)=0` Now , `|vecA + vecB + vecC|^(2)` `(vecA + vecB+vecC).(vecA + vecB+vecC)` `|vecA|^(2)+|vecB|^(2)+|vecC|^(2)` `+2(vecA.vecB + vecB.vecC+vecC.vecA)` 9+16+25+0 = 50 `|vecA + vecB +vecC|= 5sqrt2` |
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