Tuesday April 21, 2020, the Youtube channel 3Blue1Brown streamed a video lesson exploring graph of the cosine function. Was the function squared or the angle squared? What happens if we double the angle? What happens if we half the function? What do these do to our wavy cosine function?

Let us look at 6 new graphs all using the cosine function. Which two are “exact copies” except for their placement on the x-y axes? Which ones, that is, are translations of each other. **Translation means the shape, figure, graph we are considering has been moved vertically or horizontally or both.** I am **not** looking for: reflected (flipped) nor rotated (turned) nor size changed (dilated). But they might be there.

Now look at the 6 graphs below. Find the two that are translations of each other. Decide their equation or name (or color).

Once you have your decision go to this page to see the answer. Use your Back button to return here. * Answers.*

Find the cosine of 157.5 degrees or 7pi/8, without using a calculator! Use the identity above.