### Video Transcript

Which of the following is the graph
of 𝑦 equals cos of 𝑥?

Remember, one of the key features
of the cosine graph is that it has a 𝑦-intercept of one. This means we can immediately
disregard any graphs that don’t pass through the point zero, one. So, we can get rid of options (B),
(D), and (E) straightaway. Next, we know that it’s a periodic
function and that it repeats every 360 degrees. Option (C) appears to have a much
smaller period; in fact, it repeats every 120 degrees, so it can’t be this one.

This leaves only option (A). Let’s check by looking at the other
properties. Some of the roots of 𝑦 equals cos
of 𝑥 are 90 degrees, 270 degrees, and negative 90 degrees. We can see that option (A) passes
through all of these values on the 𝑥-axis. The curve has maxima at one and
minima at negative one. It is also an even function, so
it’s symmetric over the 𝑦-axis. Hence, we have confirmed that
option (A) is indeed the graph of 𝑦 equals cos of 𝑥.