You can use a graphing calc, write out a table, or use your knowledge. In this case, I will use my knowledge.
You can automatically rule out any answers with <em>sine </em>because the sin graph will never start at y=1 when x=0 (remember the unit circle and parent graphs), so rule out A. Since the graph shown is a transformation of only vertical from <em>y=cos(x)</em>, you can rule out C as well. Now you are left with B and D. B is the correct answer because if you chose D, the value for when x=0 would be y=0, while the value for x=0 for B would be y=-1, which is what you want.
