Question

Identify the maximum and minimum values of the function y = 3 cos x in the interval [-2π, 2π]. Use your understanding of transformations, not your graphing calculator.

Answer 1

@amistre64, @UnkleRhaukus, @Hero, @jhonyy9. Please help!

Answer 2

find the derivative first

Answer 3

Anyone!

Answer 4

What is the derivative?

Answer 5

derivative of y = -3sinx

Answer 6

Well what do I do to find it?

Answer 7

you didn't learn derivative?

Answer 8

She's only 14

Answer 9

I'm sure I did, but I can't remember.

Answer 10

um... then

Answer 11

lol How did yo know?

Answer 12

that's a cosine curv eright?

Answer 13

*you

Answer 14

Yes.

Answer 15

cosine curve has one cycle from -2pie to 0 and another from 0 to 2pie

Answer 16

Okay.

Answer 17

usually the highest value of cosine is 1 but since the function is scaled by 3, it'd be 3

Answer 18

Okay, and the lowest value would be -3, right?

Answer 19

yeah

Answer 20

it would go up and down between -3 and 3

Answer 21

So is that the answer? Are those the minimum and maximum values?

Answer 22

yeah but why don't u take a look at cosine and since curve

Answer 23

y = sinx and y =cosx

Answer 24

it'd make more sense afterwards

Answer 25

When it talks about the interval (-2pi, 2pi), does that affect the answer that I write?

Answer 26

if you have a shorter interval, say pie/2 to pie, your maximu value won't be three

Answer 27

bye

Answer 28

Wait! @hcmathkim! Will the interval be longer or shorter, and how do I find the maximum value and minimum value from that?

Answer 29

@Hero I really don't know what to write. Please help me.

Answer 30

Is the answer 3 and -3, or does the interval affect it?

Answer 31

highest values of cosine curve occurs at x = 2n(pie) , n = any integer

Answer 32

Just because you can't use your calc, that doesn't mean you can't imagine what it looks like in your head.

Answer 33

i meant 2n (2pie)

Answer 34

So would n be 3?

Answer 35

come on.. go look at the cosine curve..

Answer 36

it will help

Answer 37

Okay, I looked at it but I don't know how that's going to help me find the answer. I am really confused.