AP EAMCET Engineering 2018 Apr 23 Shift 2 Paper

Let the slope of the line inclined with angle 60° with the line L is n′ so,
tan‌60°=|

n−1

1+n

|
=√3
This implies,
(n−1)2=3(n+1)2
2n2+8n+2=0
The root of the above is the slope of required line. Thus the product of slopes is 1.