1.

रेखाएँ, जिनकी सदिश समीकरण निम्नलिखित है, के बीच की न्यूनतम ज्ञात कीजिए : ` vecr = (1- t ) hati + ( t - 2) hatj + ( 3- 2t ) hatk ` और ` vec r = ( s + 1 ) hati + ( 2s - 1 ) hatj - ( 2s + 1 ) hatk `

Answer» The given equations can be written as
`vec (r ) =(hat(i) -2hat(j) + 3hat(k)) + t (-hat(i) +hat(j) -2hat(k)) ` and
` vec(r ) =(hat(i) -hat(j) -hat(k)) + s (hat(i) +2hat(j) -2hat(k))`
Comparing the given equations with the standard equations
`vec( r) = vec(a)_(1) + t vec(b)_(1) " and " vec(a)_(2) + s vec(b)_(2) ` we get
`vec( a)_(1) =(hat(i) -2hat(j) +2hat(k)), vec(b)_(1) =(-hat(i) +hat(j) -2hat(k))`
`vec(a)_(2) =(hat(i)- hat(j)-hat(k)) " and " vec(b)_(2) =(hat(i) +2hat(j) -2hat(k))`
`:. (vec(a)_(2) -vec(a)_(1)) =(hat(i) -hat(j) -hat(k)) =(hat(i) -2hat(j) +3hat(k)) =(hat(j) -4hat(k))`
and `(vec(b)_(1)xx vec(b)_(2)) =|{:(hat(i),,hat(j),,hat(k)),(-1,,1,,-2),(1,,2,,-2):}|`
` =(-2 +4) hat(i) -(2+2) hat(j) + (-2 -1) hat(k)`
`=(2hat(i)- 4hat(j)-3hat(k))`
`:. |vec(b)_(1)xx vec(b)_(2)| =sqrt(2^(2)+(-4)^(2) +(-3)^(2))=sqrt(29)`
`:. SD =|((vec(a)_(2)-vec(a)_(1)).(vec(b)_(1)xxvec(b)_(2)))/(|vec(b)_(1)xx vec(b)_(2)|)|`
`=(|(hat(j) -4hat(k)).(2hat(i)-4hat(j)-3hat(k))|)/(sqrt(29)) =(|0-4+12|)/(sqrt(29))`
` =(8sqrt(29))/(29) ` units


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