Choose the function whose graph is given by:

Question

anonymous · Answer

attachment

anonymous · Answer

A.	y = 3cos(x)
 		B.	y = 3cos(x)
 		C.	y = 3cos(4x)
 		D.	y = -3cos(4x)

anonymous · Answer

this is confusing to me because i have no graphing calculator

anonymous · Answer

Google (GraphCalc). It is free and an AWESOME graphing calculator for computer.

anonymous · Answer

It does stuff like this.

anonymous · Answer

i've tried an online one, but i get multiple answers that look identical

anonymous · Answer

If they look identical... then they are the same answer right?

anonymous · Answer

well my question is which answer would have pi/2 on the graph the give

anonymous · Answer

why does the given graph go by decimals and pi

anonymous · Answer

An approximation for pi is 3.141...

anonymous · Answer

It would be a horizontal line with 3.141/2

anonymous · Answer

approximately

anonymous · Answer

i think you do not need a calculator for this
you already have the graph, the question is which function is it

anonymous · Answer

i know that D is not a reasonable answer

anonymous · Answer

you do not want to graph all 4 and see which one is the one you have
you can do it quickly with your eyeballs
evidently it looks just like cosine, except it is up 3 instead of up 1 so you have a 3 out front

anonymous · Answer

then from the graph, can you see what the period of the function is?

anonymous · Answer

pi/2 ?

anonymous · Answer

yes 
and that is all you need, since it is clearly not $2\pi$

anonymous · Answer

makes your only reasonable choice $3\cos(4x)$ which has amplitude 3 and period $\frac{\pi}{2}$

anonymous · Answer

of course if it was me, i would just go with C because it is C 95% of the time

anonymous · Answer

oh thank you so much i was going to choose a for some odd reason

anonymous · Answer

haha i use that method too ;P