Akshay
Last Activity: 9 Years ago
Find the intersection of ax+by=1 with 2 lines,
you will get two points, (1/(a-1) , -1/[b.(a-1)]) and (-(b+1)/[a.(b-1)] , 2/(b-1)),
To prove two point say A(x1,y1) and B(x2,y2) subtend angle
around origin, easiest way to check is using vectors,
Draw two vectors OA and OB,
OA = x1.i + y1.j,
OB = x2.i + y2.j,
Dot product, OA.OB = |OA|.|OB|.cos
,
in this question
=90, so dot product =0,
So, x1*x2 + y1*y2 = 0,
Putting x1,x2,y1,y2 you will get the answer: b(b+1) = -2a
