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    				| 1. | Find the value of `lambda` so that the vectors `vec(a)=2hat(i)-3hat(j)+hat(k),vec(b)=hat(i)+2hat(j)-3hat(k) a nd vec(c)=hat(j)+lambda hat(k)` are coplanar. | 
| Answer» The given vectors will be coplanar if `[vec(a)vec(b)vec(c)]=0`. Now, ` [vec(a)vec(b)vec(c)]=0hArr|(2,-3,1),(1,2,-3),(0,1,lambda)|=0hArr|(0,-7,7),(1,2,-3),(0,1,lambda)|=0 [R_(1)rarrR_(1)-2R_(2)]hArr(-1)(-7lambda-7)=0hArr7lambda + 7 = 0 hArr lambda=-1`. Hence, the given vectors are coplanar when `lambda=-1`. | |