If the shortest distance between the lines x+22= y+33= z-54 and x-31= y-2-3= z+42 is 383 5k, and 0k [x2 ]dx= - , where [x] denotes the greatest integer function, then 6 3 is equal to .
Answer
48
Solution
a1=-2 i-3 j+5 k, b1=2 i+3 j+4 k; a2=3 i+2 j-4 k, b2= i-3 j+2 k
b1 b2= i(6+12)- j(4-4)+ k(-6-3)=18 i-9 k, | b1 b2|=9 5
a2- a1=5 i+5 j-9 k
SD = |( a2- a1) ( b1 b2)|| b1 b2|= 90+819 5= 19 5
383 5k= 19 5 k= 32
[x2]=0 on [0, 1), 1 on [1, 2), 2 on [ 2, 32 ]
( 94<3)
03/2[x2]dx=( 2-1)+2 ( 32- 2 )=2- 2
=2 6 3=48
Answer: 48