Choose the function whose graph is given by (graph inside!)

A. y = 3cos(1/4x)

B. y = -3cos(4x)

C. y = 3cos(4x)

D. y = 3cos(pi/2x)

***still confused.. so it's a different graph now :/

Question

Choose the function whose graph is given by (graph inside!)

A.       y = 3cos(1/4x)

B.       y = -3cos(4x)

C.       y = 3cos(4x)

D.       y = 3cos(pi/2x)

***still confused.. so it's a different graph now :/

anonymous · Answer

graph :/

mertsj · Answer

This is obviously a well behaved cosine except that its amplitude is not 1 and it's period is not 2pi

mathstudent55 · Answer

The cosine function goes from y = -1 to y = 1. This has a vertical stretch of 3, so that indicates
y = 3*cos(x)

mertsj · Answer

Take her through the period calculation mathstudent

mathstudent55 · Answer

Now you need to deal with the "sqeeze" in x

anonymous · Answer

okay... so we can narrow it down now right? it HAS to be a positive 3cos right?

which leads us to either C.  y = 3cos(4x) or D.   y = 3cos(pi/2x)  right?? am i getting that part??

and what do u mean my "squeeze" ?? :/

mathstudent55 · Answer

Yes, it has to be positive 3

anonymous · Answer

okay :) what do we do next?

mathstudent55 · Answer

Normally the period of the cosine function is 2pi. That means it takes 2pi in x to see the entire look of the function. More than 2pi will create a repetition of the values of the function.

anonymous · Answer

okay.. but this one doesn't have a period of 2pi right?

mathstudent55 · Answer

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