Two lines are [b]parallel[/b] if they have the same gradient.[br][br]Two lines are [b]perpendicular[/b] if the product of their gradients is -1. In other words, if their gradients are negative reciprocals of one another: [math]m_s=-\frac{1}{m_r}[/math][br][br]In the next applet, lines r (pink) and s (sky blue) are graphed together. Modify their gradients and y-intercepts to check if the statements above are true.