- anonymous

help!!

- katieb

I got my questions answered at brainly.com in under 10 minutes. Go to brainly.com now for free help!

Get this expert

answer on brainly

SEE EXPERT ANSWER

Get your **free** account and access **expert** answers to this

and **thousands** of other questions

- anonymous

##### 1 Attachment

- anonymous

how do I write the equation of the graph?

- anonymous

Tell me what the graph of y = cos x looks like.

Looking for something else?

Not the answer you are looking for? Search for more explanations.

## More answers

- anonymous

its (0,1) (pi,-1) (2pi,1) (3pi,-1) etc

- anonymous

but with the dots in um the up and down motions (from half of 0 and pi , pi and 2pi,

- anonymous

So what is the difference between this one and cosx?

- anonymous

its sin ? and the graph is given but I don't know how to get an equation

- anonymous

nvm its cos

- ranga

The sine function is zero when x = 0.
A cosine function is 1 when x = 0.
So we need to choose the acos(bx) here.
a is the amplitude. Amplitude is how much above or how much below the mean line (which is x axis here) the curve swings. Could you figure out the amplitude from the diagram?

- anonymous

a = 3

- anonymous

so y = 3cos.. bx

- ranga

Yes. a = 3.
So the equation is y = 3cos(bx). We still need to figure out b.
The period of a cosine or a sine function is how long before the curve repeats itself. Could you look at two successive peaks in the diagram and figure out after how much x the function repeats itself?

- anonymous

every 3pi?

- anonymous

or every 6pi/2?

- ranga

No. The curve attains a peak at x = 0. The next peak occurs at x = 6pi.
The period is how much x has passed before the curve starts to repeat itself.
So what is the x distance between peak-to-peak?

- anonymous

6pi/2

- ranga

No. At x = 0, first peak. At x = 6pi the next peak.
The difference in x is: 6pi - 0 = 6pi.
Every 6pi the curve repeats itself. You can take the distance between two successive low points also and it will still be 6pi.
So the period of this curve is 6pi.

- anonymous

OH

- anonymous

y=3cos (6pi)x ?

- ranga

The formula for the period of cos(bx) is: Period = 2pi / b
Looking at the graph we found the period to be 6pi. Plug that into the formula:
6pi = 2pi / b
Find b.

- anonymous

2pi/6pi = pi/3pi

- ranga

The pi will cancel out. so b = ?

- anonymous

yes sorry

- anonymous

1/3

- ranga

Yes. Put them all together and the curve represented in the graph is: y = 3cos(1/3*x)

- anonymous

okay thank you!! a lot!

- ranga

You are welcome.

Looking for something else?

Not the answer you are looking for? Search for more explanations.