The expression b ⊥ c says that b and c are perpendicular. Let's draw the diagram and then we can reason about it.
According to the Lines Perpendicular to a Transversal Theorem, in a plane, if two lines are perpendicular to the same line, then they are parallel to each other. From the diagram, we see that c and d are both perpendicular to a. Therefore we can say that c ∥ d.
Next, according to the Perpendicular Transversal Theorem, in a plane, if a transversal is perpendicular to one of two parallel lines, then it's perpendicular to the other line. Therefore, we can finally say that b⊥ c.
