Show that the lines x = - y = 2z and x + 2 = 2y – 1 = - z + 1 are perpendicular to each other.
HINT: The given lines are 
and 
Given – 
& 
To prove – The lines are perpendicular to each other
Direction ratios of L1 = (2,-2,1)
Direction ratios of L2 = (2,1,-2)
Tip – If (a,b,c) be the direction ratios of the first line and (a’,b’,c’) be that of the second, then the angle between these pair of lines is given by 
The angle between the lines
Hence, the lines are perpendicular to each other.
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