Show that the lines 
and 
are at right angles.
Given : the lines 
and 
.
To prove : the lines are at right angles.
Formula used : If the lines are 
= 
= 
and 
= 
= 
then the angle between the lines ‘θ’ is given by
θ = 
The lines 
and 
.
Here p = 7 , q = -5 , r = 1 and l = 1 , m = 2 , n = 3
θ = 
= 
θ = 
= 
= 90°
θ = 90°
The Lines 
and 
are at right angles.
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