# Thread: Factoring and calculator issues

1. ## Factoring and calculator issues

hey everyone,
i have a calc 2 test coming up on taylor polynomials and power series. when i type in the convergence points in the original equations, i sometimes have to input (-1)^"variable" for some reason, the calculator spits out an answer with sin and cosines that take up the entire screen. for example, (-1)^x*(-1)^x puts out 2COS(180X)^2-1+2SIN*(180X)...blablabla...i tried every combination of settings but it still gives me the same BS answer. i know this is simple algebra, but some equations are super long and i want to use the calc to do it for me.

does anyone have any idea why this is happening?

thanks!

2. ## Re: Factoring and calculator issues

Some teachers design questions so that someone with a ti-89 will have little advantage over someone with a 4 function calculator. I found that most of calc 2 could be done faster by hand, and perhaps just checked on the calculator.

Calculators can get really messy when dealing with trig functions. Because of all the trig identities and how they are all practically just restatements of eachother, you can represent a trig expression in a ton of ways. The calculator doesn't differentiate between them very well.

3. ## Re: Factoring and calculator issues

i've encountered that in high school, but the example problem i wrote down is simple algebra, i cant figure out why the calculator is making such a big issue over multiplying exponents...These types of exponents are common with taylor polys and i just wanted a quick way to solve them. i guess ill just have to use my iphone and wolfram alpha...what a waste of 150\$ on this nspire calc..

4. ## Re: Factoring and calculator issues

Could you give me the specific problem, not just the calculator output?

5. ## Re: Factoring and calculator issues

whenever i try to enter a negative number ^ a variable and try to multiply it.

for example= (-1)^x * (-1)^x

Thanks!

6. ## Re: Factoring and calculator issues

One thing you may note is that (-1)^x*(-1)^x = (-1)^(2x) Since 2x is always even and a negative number raised to an even power is positive, you could try inputting 1^2x instead, which is just 1 for all values of x.

It's hard for me to point to the particular problem since I don't have the n-spire. But hopefully that helps.

7. ## Re: Factoring and calculator issues

Also, are you telling your calculator to do an infinite approximation, because if so, the taylor series would have infinite terms. (not specifying the degree of approximation should default to infinite) There should be a place where you can put a parameter that tells it to approximate to a certain degree.

8. ## Re: Factoring and calculator issues

here is where my issues originate:
ImageShack® - Online Photo and Video Hosting

or

http://desmond.imageshack.us/Himg163...gif&res=medium

i tried to factor the beginning of the equation, i did not try to use the summation command, just wanted to get everything factored down to n, as is shown in the last step. my issue is not with calc or taylor polys, just the way that the calc handles algebra.

I'm horrible at algebra and this would take me a good while to factor if i tried to do it by hand.

thanks!

9. ## Re: Factoring and calculator issues

I'm not sure what you're looking for. I could give you a quick overview of factoring, but I can't really help too much with the calculators. The bottom line is that they aren't very good at outputting clean functions and can't solve all of our problems yet. If they were, only mathematicians and physicists would need to know upper level math and engineers would just need a calculator.

10. ## Re: Factoring and calculator issues

i pretty much gave up trying to use the calc to factor it lol.

if you could provide a method to factor one of the equations i posted above, i will be very grateful!

11. ## Re: Factoring and calculator issues

In the second one, all they did was cancel 4^n on top and 4^n on bottom. It's not even factoring.

The first one involves some factoring, but only a minimal amount.

[IMG]http://latex.codecogs.com/gif.latex?(-4)^n%20=%20(-1*4)^n=(-1)^n*(4)^n[/IMG]

Do you see where they did this step? That 'technique' along with basic cancellation should cover most of your problems that are caused by (-1)^n.

12. ## Re: Factoring and calculator issues

thanks, i think i got it. i sometimes get much larger equations when doing the Ratio test with series problems that trip me up constantly. I understand the theories behind calculus very well, it's just the basic math that i have major problems with.