Functions

[little_katie]

i can't figure out this question here it is :
what equation of the form y=acosx+d best models the following data:

X 0 - pie/2 - pie -3pie/2 -2pie
y -1 2 5 2 -1

i need full reasons , and not just this is the right one.

 

[stapel]

Try drawing the dots, and roughing in a cosine curve.

What is the difference between the highest and lowest spots? So what is the amplitude? This gives you the value of "a", up to sign. (If the cosine is "upside down", then make "a" negative.)

What is the center line for the cosine curve? Does it coil itself back and forth across the x-axis, or is there an upward or downward shift? If there is a shift, which way, and by how much? This gives you the value of "d".

Eliz.