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    				| 1. | Find the area aparallelogram whose diagonals are ` vec a=3 hat i+ hat j-2 hat ka n d vec b= hat i-3 hat j+4 hat kdot`A. `7sqrt(3)` sq unitsB. `5sqrt(3)` sq unitsC. `3sqrt(5)` sq unitsD. none of these | 
| Answer» Correct Answer - B `(vec(d_(1))xxvec(d_(2)))=|(hat(i),hat(j),hat(k)),(3,1,-2),(1,-3,4)|=(4-6)hat(i)-(12+2)hat(j)+(-9-1)hat(k)` `=(-2hat(i)-14hat(j)-10hat(k)) ` `rArr|vec(d_(1))xxvec(d_(2))|=sqrt((-2)^(2)(-14)^(2)+(-10)^(2))=sqrt(300)=10sqrt(3)` `rArr` area of the ||gm `=(1)/(2)|vec(d_(1))xxvec(d_(2))|=5sqrt(3)` sq units. | |