Question

Need help with precaluclus will give owlbuck

Answer 1

lol

Answer 2

this one is probably my hardest looking one , well for me

Answer 3

@inkyvoyd please help us. :P

Answer 4

lol

Answer 5

oh is nnesha!

Answer 6

with like the best baby pictures i love them

Answer 7

yea lol I like them too.

Answer 8

double angle formula
co(2x) = 2cosx^2-1
use that and then you will get quadratic equation

Answer 9

Ehm. wait which one is that cos the first one

Answer 10

I am wondering the same

Answer 11

cos(2x) =1-2sin^2x `or` 2cos^2-1
and look at the 2nd term which is cos x so you should use 2nd one

Answer 12

-cry-

Answer 13

man im sorry lol, I failed in helping.

Answer 14

thats ok lol, u helped me not to bad in the last one

Answer 15

the 2nd term is cos(x) so it would be great if you use 2cos^2-1
there are different ways to prove/verify the identity we should figure out which one is best for each question

Answer 16

im just trying to learn now lol

Answer 17

oh ok that makes sense. Can i use that for the first term too, 2cos^2-1 for cos2x

Answer 18

Nnesha has helped by providing a review of the identity co(2x) = 2cosx^2-1 .
Substitute co(2x) = 2cosx^2-1 for cos 2x in the original equation, and then write out the whole thing.

Answer 19

wait what is co

Answer 20

In other words, write out cos 2x + cos x = 0, making that substitution discussed above.

Answer 21

is it short for cos?

Answer 22

Yes, sorry. cos, not co. ;(

Answer 23

oh ok np

Answer 24

1-sin^2x +2xcos^2-1+

Answer 25

As you yourself have typed in, 2cos^2-1 can be substituted for cos2x.
Why bring in the sine function?

Our goal (not stated) was to eliminate all of the trig functions except for cos x.

Answer 26

o sorry i thought it was cos2x and second one was for cosx

Answer 27

2cos^2-1 for cos2x results in

2cos^2-1 + cos x = 0, right?

Answer 28

right

Answer 29

yes

Answer 30

Now we have only one trig function, cos x.

This equation just happens to be a quadratic equation as well as a trig equation.

Rearrange the terms in DESCENDING order of powers of cos x.

Answer 31

lol

Answer 32

nvm i think i got this. so cosx goes first?

Answer 33

yea I think so

Answer 34

is it mathmale?

Answer 35

That's not the whole story. You have no trig function here except for the cosine.

What is the highest power of the cosine function you see?

Answer 36

^2-1

Answer 37

2cos^2-1 + cos x = 0

You need to look at 2cos^2 alone. This is "twice the square of the cosine function."

Answer 38

^2

Answer 39

So, your equation begins with \[2\cos^2 x\]

Answer 40

this is what I meant when I asked you for the term representing the highest power of x.

Answer 41

Now, what is the next highest power of x?

Answer 42

oooo, ok

Answer 43

cos x

Answer 44

Yea!

Answer 45

wel and the -1

Answer 46

and what's the coefficient of that power of cos x?

Answer 47

-1

Answer 48

is it -1?

Answer 49

So then you end up with \[2\cos^2 x - 1\cos x\]

Answer 50

awesome

Answer 51

oh I see

Answer 52

how do you complete this equation? Which term in the original equation have we not yet used? Find it and then complete the whole equation ...... = 0.

Answer 53

[0,2pi)

Answer 54

pie

Answer 55

yea

Answer 56

wait what do those brackets and parenthesis mean

Answer 57

i forgot

Answer 58

2cos^2-1 + cos x = 0 becomes what?
Mark: please hold the pie and all jokes and comments for now, OK?

Answer 59

lol

Answer 60

I wasn't joking lol, I am actually trying to learn, good job with the teaching I love it.

Answer 61

yes i dont think he was joking

Answer 62

no, I was trying to be serious here.

Answer 63

but honestly i dont know it becomes 2pi?

Answer 64

2cos^2-1 + cos x = 0 needs to be rearranged in descending powers of cos x.

Mark: You're welcome to observe. Unless matlee has a question or comment for you, please remain in the background.

Answer 65

2cos^2-1 + cos x = 0 needs to be re-written, as explained earlier. pi, 2pi have nothing to do with this operation.

Answer 66

square root?

Answer 67

lol cmon mathmale don't be so harsh with me, because I tend to understand when I communticate. If you want me to leave then I will, but I am wanting to be part of this.

Answer 68

holy crap i subtract it

Answer 69

Wait. Stop. First, before you do anything more, tell me what you think our objective is.

Answer 70

lol my brothers computer so slow

Answer 71

Ok uhm, to make an exact value

Answer 72

Ok, I guess I will just leave, but matlee good luck. I believe you can do this.

Answer 73

No. Our objective is to write this equation by descending powers of cos x.

Here's an example of descending order: 10 8 7 6 3 2 1

Answer 74

Thank you i will see you soon

Answer 75

;)

Answer 76

Ohhhhh

Answer 77

Rewrite in descending order by powers of cos x;

Answer 78

-1cosx + 2cos^2= 0 i was like whatt

Answer 79

You've written this with ASCENDING powers of cos x.

What we need is
\[2\cos^2 x + \cos x -1 = 0\]

Answer 80

.. . which has its powers of cos x DESCENDING.

Answer 81

What would be our next goal? If necessary, go back and read the problem statement / instructions.

Answer 82

wait what where did u get that extra x

Answer 83

The goal of this problem is to ...... " Please finish this sentence.

Answer 84

to find all solutions in t he interval [0,2pi)

Answer 85

Honestly, there is NO extra x. Which occurence of x are you rreferring to?

Answer 86

2cosx i thought it transtalted to 2cos^2

Answer 87

No, it doesn't.

First term is 2 cos^2 x. "Two times the square of cos x."

Answer 88

Second term is +cos x.

Third term is -1.

Answer 89

ok

Answer 90

Be careful about assumptions. Don't automatically assume something if you're not sure; check it out!

Answer 91

\[2\cos^2x + \cos x - 1 = 0\]

Answer 92

is the equation we have to solve FIRST for cos x and SECOND for x.