Find shortest distance between the line
`vecr = (5hati + 7hatj + 3hatk )+lambda (5hati-6hatj+2hatk)and vecr = (9hati+13hatj+15hatk)+s (-3hati+hatj-hatk)`

Explanation

The distance between two lines
`vecr = veca_(2)+lambda vecb_(1) and vecr = veca_(2)+muvecb_(2)`
is given by
`d= abs(((veca_(2)-veca_(1))cdot(vecb_(1)xxvecb_(2)))/(abs(vecb_(1)xxvecb_(2))))`
`=abs(((4hati+6hatj+12hatk)cdot(4hati-hatj-13hatk))/(sqrt(186)))` `vecb_(1)xxvecb_(2)=abs[[hati, hatj,hatk],[5, -6, 2],[-3,1,-1]]`
`=abs(16-6-156)/(sqrt(186))` `=4hati - hatj-13hatk`
`=146/sqrt(186)`