9. A navigation light on a point in a lake flashes 1 s on and 1 s off. After three flashes, the light stays off for an extra 2 s. a. Let 1 represent "on" and 0 represent off." Sketch a graph with time on the horizontal axis to represent the
flashing of the light. Include three cycles.
b. Explain why this pattern is periodic.
c. What is the period of the pattern?
d. What is the amplitude?

Please help.

Which statement explains how you could use coordinate geometry to prove the opposite sides of a quadrilateral are congruent? a. use the slope formula to prove the slopes of the opposite sides are the same. b. use the slope formula to prove the slopes of the opposite sides are opposite reciprocals. c. use the distance formula to prove the lengths of the opposite sides are the same. d. use the distance formula to prove the midpoints of the opposite sides are the same.