1.

Find the area of a parallelogram whose adjacent sides are given by the vectors ` -> a=3 hat i+ hat j+4 hat k`and ` -> b= hat i- hat j+ hat k`.A. `sqrt(42)` sq unitsB. 6 sq unitsC. `sqrt(35)`sq unitsD. none of these

Answer» Correct Answer - A
`(vec(a)xxvec(b))=|(hat(i),hat(j),hat(k)),(3,1,4),(1,-1,1)|=(1+4)hat(i)-(3-4)hat(j)+(-3-1)hat(k)=5hat(i)+hat(j)-4hat(k)`.
Required area `=|vec(a)xxvec(b)|=sqrt(25+1+16)=sqrt(42)`sq units.


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