# Precalculus Help...I know, I'm a noob :(

### #1

Posted 08 March 2006 - 01:45 AM

here's a problem i'm stuck on:

simplify this...

1 - [ (cot^2 X + cot X) / (cot^2 X - 1) ] + 3

the answer should be either 3cotX - 4 or (3cosX - 4sinX) / (cosX - sinX)

the thing is, i have to show work, so i need help

if anyone is willing, thanks!

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### #2

Posted 08 March 2006 - 02:06 AM

Ok...anyway, i'm probably sure i'm just not thinking of the right "combination" for lack of a better word...

here's a problem i'm stuck on:

simplify this...

1 - [ (cot^2 X + cot X) / (cot^2 X - 1) ] + 3

the answer should be either 3cotX - 4 or (3cosX - 4sinX) / (cosX - sinX)

the thing is, i have to show work, so i need help

if anyone is willing, thanks!

1=> 1 - [ (cot^2 X + cot X) / (cot^2 X - 1) ] + 3

2=> 4 - [ (cot^2 X + cot X) / (cot^2 X - 1) ]

3=> 4 - [ {cotx(cotx + 1)} / (cotx + 1)*(cotx - 1) ]

4=> 4 - [ cotx / (cotx -1) ]

5=> [4cotx - 4 - cotx] / [cotx - 1]

6=> [3cotx - 4] / [cotx - 1]

7=> [(3cosx - 4sinx) / sinx) / (cosx - sinx) / sinx

8=> (3cosx - 4sinx) / (cosx - sinx)

edit: if you can't see what I did on a step, let me know.

### #3

Posted 08 March 2006 - 02:06 AM

Good luck.

### #4

Posted 08 March 2006 - 02:14 AM

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### #5

Posted 08 March 2006 - 02:19 AM

Multiplied that 4 out front up and down by (cotx - 1) so the whole thing would be over the same denominator.wait what did you do b/t steps 4 and 5?

### #6

Posted 08 March 2006 - 02:23 AM

i didnt see that the bottom could be factored out until you showed me...i knew there was something i missed

thanks!

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### #7

Posted 08 March 2006 - 02:33 AM

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### #8

Posted 08 March 2006 - 02:35 AM

Sure, no problem.ohhhhhhhh, ok thanks, jmcc!

i didnt see that the bottom could be factored out until you showed me...i knew there was something i missed

thanks!

edit:

As my teacher says "I'm not sure, maybe I can do these." He's a pretty big smartass for such an old guy. But sure, what's the problem.willing to tackle another one? haha

### #9

Posted 08 March 2006 - 02:41 AM

(sin^3 X - cos ^ 3 X) / (1 - sin^2 X cos^2 X)

i simplified it all the way down to:

(sinX - cosX) / (1- sinX cosX) (1 + sinX cos X)

but i dont know what to do next

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### #10

Posted 08 March 2006 - 02:50 AM

What's it supposed to look like at the end?the problem is:

(sin^3 X - cos ^ 3 X) / (1 - sin^2 X cos^2 X)

i simplified it all the way down to:

(sinX - cosX) / (1- sinX cosX) (1 + sinX cos X)

but i dont know what to do next

### #11

Posted 08 March 2006 - 02:53 AM

or

1 + sinXcosX

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### #12

Posted 08 March 2006 - 03:38 AM

Sorry this took so long, I was being a dope about it. Did you see how you do it yet? Split the top up as a difference of cubes. Then take the 3 term poly and change (sinx)^2 into 1-(cosx)^2 (or do the sin squared like that, too) which gets that 3 term down to 1 + sinxcosx. Then you can eliminate and you're left with (sinx - cosx) / (1 - sinxcosx).(sinX - cosX) / 1 - sinXcosX

or

1 + sinXcosX

### #13

Posted 08 March 2006 - 04:01 AM

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### #14

Posted 08 March 2006 - 04:17 AM

sinx^3 - cosx^3 / 1 - sinx^2cosx^2

Top: sinx^3 - cosx^3

= (sinx - cosx)(sinx^2 + sinxcosx + cosx^2)

= (sinx - cosx)(sinx^2 + sinxcosx + [1 - sinx^2])

= (sinx - cosx)(1 + sinxcosx)

Bottom: (1 - sinx^2cosx^2)

= (1 - sinxcosx)(1 + sinxcosx)

So the (1 + sinxcosx)'s on top and bottom cancel and you're left with (sinx - cosx) / (1 - sinxcosx).

### #15

Posted 08 March 2006 - 04:22 AM

### #16

Posted 08 March 2006 - 04:27 AM

It's the same base identity, so any way you want to write it is fine. I prefer to take more steps. Helps me keep straight what I'm doing. Guards me against the little errors I make.Converting (cos x)^2 into 1 - (sin x)^2 is a waste of time, it would of be easier to reconized that (cos x)^2 + (sin x)^2 = 1.

### #17

Posted 08 March 2006 - 12:11 PM

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### #18

Posted 09 March 2006 - 03:17 AM

And i'm going to use this...

### #19

Posted 09 March 2006 - 03:23 AM

I was helping out someone else with precalc today. Seeing degrees again was a trip, because they don't really come up after you learn to use radians. Stupid crappy degrees...Were almost about to do the shit your doing right now, were doing the Circle where 360 degrees = 2pie.

And i'm going to use this...

### #20

Posted 09 March 2006 - 03:47 AM

Were almost about to do the shit your doing right now, were doing the Circle where 360 degrees = 2pie.

And i'm going to use this...

yea, in about 2 or 3 weeks, you will need this

haha...when are we gonna play street 3???

you're always on splinter cell and never leave

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### #21

Posted 09 March 2006 - 03:48 AM

I was helping out someone else with precalc today. Seeing degrees again was a trip, because they don't really come up after you learn to use radians. Stupid crappy degrees...

yea, my teacher is trying to deviate away from degrees into radians and pi radians...thanks for the help, jmcc...he doesnt collect homework, but when we went over it in class today, nobody got more than 4 of the questions (out of 9) except for me (with your help ) i got 5 on my own and the 2 you helped me with...so i only needed help with 2 more

thanks again!

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### #22

Posted 09 March 2006 - 11:17 PM

yea, in about 2 or 3 weeks, you will need this

haha...when are we gonna play street 3???

you're always on splinter cell and never leave

Sorry bro, definitely soon, but I got grounded for coming home late past my curfew so it might be a while.

I've always asked my teachers "when am I going to use this? Why next year!" That's always the answer I get.

I'm barely getting an A in Pre-Cal not fun. Oh ok, here we go, the tan x = sinx/cosx, see that thing we taught you Tangent = Opposite/Adjacent! Screw that! It's now sin/cos!!!!

I hate also when lets say 45 degrees is root 2 over 2 or something, shit's reeeeetarded.

### #23

Posted 09 March 2006 - 11:56 PM

SOH-CAH-TOA will help you a lot.Sorry bro, definitely soon, but I got grounded for coming home late past my curfew so it might be a while.

I've always asked my teachers "when am I going to use this? Why next year!" That's always the answer I get.

I'm barely getting an A in Pre-Cal not fun. Oh ok, here we go, the tan x = sinx/cosx, see that thing we taught you Tangent = Opposite/Adjacent! Screw that! It's now sin/cos!!!!

I hate also when lets say 45 degrees is root 2 over 2 or something, shit's reeeeetarded.

And if you're going to become an engineer or any science, you'll definitely be using these things later.

### #24

Posted 10 March 2006 - 12:14 AM

there's a little math involved in cinematography, but nothing complicated so far. i'm sure you'll need math if you do anything financial or scientific, but otherwise just knowing how to balance a checkbook seems to be the most math intensive activity for the average person.

### #25

Posted 10 March 2006 - 12:48 AM

any science, you'll definitely be using these things later.

yea, i'm lookin into science...

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### #26

Posted 10 March 2006 - 01:31 AM

SOH-CAH-TOA will help you a lot.

And if you're going to become an engineer or any science, you'll definitely be using these things later.

Yeah i know that SOH CAH TOA stuff, it's easy.

In Chemistry I really haven't used radians or degrees funny enough, being in Biology, Physics, and Chemistry and next year not taking a science I haven't used much math.

I guess Stoicheimoetrey is where it gets tricky but that's simple math.

### #27

Posted 10 March 2006 - 03:35 AM

I would have been able to answer a couple months ago, but that was last semester. My brain can only handle so much math, and right now it's on matrices.

Good luck.

I hope you don't take analytical geometry and calculus. You have to know your trig, your geometry and algebra, and the calculus which my instructor says "ties it all together".

R.I.P

Curious George

2003-2005