Graphing y=cos^2(x) - Trig Graphs

[tycon69]

We had a test recently in trig on graphing trig functions. I found it all quite simple except a problem that we had not discussed. I believe the problem was something like y=cos^2(x). I graphed it by squaring each cosine value, because i had no idea what else to do, but when i turned the test in, my teacher told me that it was only half correct. I ended up with a nice M (maybe W) shape. Thinking back, would it have been correct to change the equation to y=(1+cos2x)/2 and then graph it?

 

[symbolipoint]

tycon69, what are you trying to express? Are you asking about [cos(x)]*[cos(x)], or what? You seem to mean just that. All the values will be positive (the 'y' values). The 'M' shape that your teacher indicated. The amplitude is 1.

 

[Werg22]

Maybe you took the squares of negative cosines as negative? cos^2(x) is greater than 0 everywhere, was your graph?

 

[tycon69]

yes it was, it's amplitude was one and everything was above 0. I just graphed it on a graphing application and the graph is identical to what i graphed. I must have overlooked a simple mistake, i'll have to look at it monday. Luckily she only counted off half so i ended up with an A. Thx for trying to help me, i know my explanation was quite confusing.

 

[HallsofIvy]

We had a test recently in trig on graphing trig functions. I found it all quite simple except a problem that we had not discussed. I believe the problem was something like y=cos^2(x). I graphed it by squaring each cosine value, because i had no idea what else to do, but when i turned the test in, my teacher told me that it was only half correct. I ended up with a nice M (maybe W) shape. Thinking back, would it have been correct to change the equation to y=(1+cos2x)/2 and then graph it?

What was the problem? Just to graph the function?

 

[tycon69]

Yes, the problem was just to graph the function. I found out it was a pretty stupid mistake on my part in that i graphed cos(0)=0 when it should have of course been 1