Given l₁ : r₁ (t) = i tj, l₂ : r₂ (u) = j u (i j) , find the point where l₁ and l₂ intersect and find the angle between l₁ and l₂ .
a. point (1, -1, 0) θ = 2π/3
b. point (1, 1, 0) θ = π/3
c. point (1, 2, 0) θ = π/4
d. point (1, -1, 0) θ = 3π/4