PhyFl18SS1.7.5 Sheet 1.9.5 The birth of the cosine function. That’s all sines and cosines are. They are circular motion spread out over time. Actually, they are one dimension of that circular motion spread out over time. In this case here, the vertical component of the circular motion is laid out over time. See the animation on my website. If you can get this one thing down it will make physics and math so much easier for you.