The angle between lines 3x+y=1 and x+3y=1 is
(1)
Given equations of lines are
3x+y=1 ...(i) and x+3y=1 ...(ii)
Let m1 and m2 be slopes of (i) and (ii), then
m1=-3, m2=-13
Let θ be the angle between them, then
tanθ=|m1-m21+m1m2|=|-3+131+3·13|=|-3+123|=13⇒ θ=π6