Suppose τₙ₁ and τₙ₂ are stress vectors acting on planes with unit normals n₁ and n₂ respectively and passing through a point with stress state. Show that the component of τₙ₁ is:
a) τₙ₁ cos(θ)
b) τₙ₁ sin(θ)
c) τₙ₁ tan(θ)
d) τₙ₁ cot(θ)