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Find the equations of a line passing through the point P(2,-1,3) and perpendicular to the lines `vec(r ) =(hat(i) + hat(j) -hat(k)) +lambda (2hat(i) -2hat(j) +hat(k))` and `vec( r) =(2hat(i) -hat(j) -3hat(k)) +mu (hat(i) +2hat(j) +2hat(k))` |
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Answer» The given lines are `vec(r) =vec(a)_(1) +lambdavec(b)_(1) ......(i)" where " vec(a)_(1)=(hat(i) +hat(j) -hat(k)) " and " vec(b)_(1) =(2hat(i) -2hat(j) +hat(k))" and "` `vec(r ) =vec(a)_(2) +lambda vec(b)_(2) .....(ii) " where "vec(a)_(2) =(2hat(i) -hat(j) -3hat(k)) " and " vec(b)_(2) =(hat(i) +2hat(j) +2hat(k))` The required line is perpendicular to (i) as well as (ii) . Also (i) is parallel to `vec(b)_(1) ` and (ii) is parallel to `vec(b)_(2)` So the required line is perpendicular to both `vec(b)_(1) " and " vec_(b)_(2)` Consequently this line must be parallel to `(vec(b)_(1)xx vec(b)_(2))` Now , `(vec(b)_(1) xx vec(b)_(2)) =|{:(hat(i),,hat(j),,hat(k)),(2,,-2,,1),(1,,2,,2):}| =(-6hat(i) -3hat(j) +6hat(k))` So we have to find the equation of a line passing through the point P(2,-1,3) and parallel to `(vec(b)_(1)xx vec(b)_(2))` Hence the required equation is `vec( r) =(2hat(i) -hat(j) +3hat(k)) + t (-6hat(i) -3hat(j) +6hat(k)) where t is an arbitrary constant. |
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