Question

What is the period of the function?
y = 4 cos (2π x)

Answer 1

@SolomonZelman

Answer 2

In general, we have this cosine equation

y = A*cos(Bx - C) + D

Answer 3

The period T is

T = 2pi/B

Answer 4

thanks for helping me, let me look at what you wrote hang on

Answer 5

okay yes I remember learing that

Answer 6

what is the value of B in this case?

Answer 7

is it 4?

Answer 8

B is the term in front of the x

Answer 9

y = A*cos(Bx - C) + D

Answer 10

oh then that's 1, b=1

Answer 11

so 2pi/1 = 2pi

Answer 12

y = A*cos(Bx - C) + D
y = 4*cos(2pi*x - 0) + 0

Answer 13

look again

Answer 14

4 ?

Answer 15

the 4 matches up with the A

Answer 16

what matches up with the B?

Answer 17

no I mean I tired to solve the equation, =4. but matches up with b? what do you mean? im sorry im a little confused

Answer 18

2pi matches with b

Answer 19

so B = 2pi

Answer 20

T = 2pi/B

T = 2pi/2pi ... plug in B = 2pi

T = 1

Answer 21

it sure does

Answer 22

So the period is 1

Answer 23

ahh I see

Answer 24

In other words, the function repeats itself every 1 unit (say it has a peak at x = 2, it would have another peak at x = 3, then another at x = 4, etc etc)

Answer 25

is that how I find all the periods? I mean with this sort of equation. the one you posted

Answer 26

yes if you know the equation, you use a template like this

Answer 27

can you help me with more qustions? or are you busy?

Answer 28

it's slightly different with tangent functions though since it has a period of T = pi/B

but it's the same with sine or cosines

Answer 29

I can do one more

Answer 30

which represents the reference angle for 5pi/6

Answer 31

where is that angle? which quadrant?

Answer 32

that's all the question says :/

Answer 33

do you know how to convert that angle to degrees?

Answer 34

not exactly, remind mee

Answer 35

you multiply the radian angle by 180/pi

Answer 36

esay enough

Answer 37

so what is the radian angle...

Answer 38

is it 6?

Answer 39

5pi/6 is the entire radian angle

Answer 40

(5pi/6)*(180/pi) = ???

Answer 41

150 !

Answer 42

good

Answer 43

where is 150 degrees?

Answer 44

is that in the angel? sounds like an angel to me

Answer 45

I mean in a triangle

Answer 46

150 degrees is an angle

which quadrant is it in?

Answer 47

im not quite sure I remember what a quadrant is

Answer 48

http://www.mathsisfun.com/definitions/quadrant-graph-.html

Answer 49

and here is the unit circle

http://www.mathsisfun.com/geometry/unit-circle.html

Answer 50

gahh okay let me take a looksie

Answer 51

well its a positive number so a positive quadrent, how do I know if its x or y?

Answer 52

quadrent 1

Answer 53

forget my last question haha

Answer 54

do you see where 0 degrees is? and 90 degrees?

Answer 55

yes

Answer 56

where is 90 degrees, mark it on this drawing

Answer 57

click on the pencil to draw on my drawing