Question about Texas Instruments TI-89 Calculator

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Log & reciprocal functions

I can't find lo and reciprocal functions tabs.

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  • Anonymous Oct 27, 2008

     i dont not know where to access the reciprocal function on the TI-89

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There is no log (base 10) button on a TI-89. It's buried in the CATALOG as log(. As a shortcut, you can do ln(#)/ln(base), where # and base are replaced with what you want. For the inverse of a log, do the base raised to the part on the other side of the equals sign. So, log(x) = 2 would become 10^2 = x.

Posted on Oct 04, 2009

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It's the second function of the "2" key, marked "x-superscript-negative-one".

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Im pressing the buttom that everyone is saying is the inverse key but it is saying error. i really need help with this.


It is much more enlightning to tell us what you want to do rather than talk about something that does not exist. And one thing that does not mean anything is that ellusive INVERSE key that everyone and his dog is looking for.
The additive inverse of a number a is its opposite (-a). The key to use is the change key (-).
The multiplicative inverse of non-zero number a is its reciprocal 1/a
The inverse of the natural log (LN) function is the EXPONENTIAL function e^(x). On most calculators if one function is accessed diectly (the marking is on the key), its inverse is accessed by pressing [SHIF] (Casio, or [2nd] (TI) or [2ndF] (Sharp).
The inverse of the function raise 10 to a power [10^x] is [LOG]
Similarly, the inverse of the sine function SIN is the arcsine [sin^-1]. To access the latter, it you press [2nd][SIN]. The same is true for arcosine [2nd][COS], and arctangent [2nd][TAN]

The inverse of the square functions [x^2] is the square root function [2nd][x^2]
Inverse of x^3 is cubic root
This is just a quick overview.

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Where is the inverse button on the casio fx-82ES


For the reciprocal of a number, enter the number then press the key marked with an x^-1. You might have to use the SHIFT key first. For inverse of trigonometric functions use the SHIFT key followed by the function name. The inverse of LN is e^x. The inverse of log is 10^x. To calculate the inverse of a matrix, enter the name of the (already created) square matrix then press x^-1.

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Find a calculator approximation for each circular function value. csc (-9.4946) The answer in the solutions manual is 14.3338 by imputing sin (-9.4946) = .0698 ans^-1 approx. 14.3338 ?


I am not sure if there really is a question here. The cosecant function is defined as the reciprocal of the sine function : csc(x)=1/sin(x)
You can calculate two ways. [ ] is a single key press, [(-)] is the change sign key.

csc(-9.4946)=1[/][sin] [(-)] 9.4946[)] [EXE]

The other way is to just calculate sin(-9.4946). the result will be stored in ANS memory. At this time, if you press the key [x^-1] you are calculating the reciprocal of the result stored in ANS.

Both methods yield the same result.

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1 Answer

I have to take the secant of -1.2. I'm supposed to get a degree. I can't figure out the order to push buttons. PLEASE help!


TWO THINGS YOU NEED TO KNOW, Eli.

1. Secant will NEVER return a degree measure (or even a radian measure) no matter what computer or calculator you use. The reason is because secant returns the ratio of sides (hypotenuse over adjacent), which has a range of [1, infinity). So, to put this in basic math terms: all six trig functions have ANGLE INPUTS (degrees & radians) while spitting out SIDE-RATIO OUTPUTS (for instance, the height of the tree in relation to the distance away from it).

2. DEGREE MODE: All the TI calculators I've ever used have a way to switch between RADIAN mode & DEGREE mode. If you're taking pre-calc or trigonometry I'd suggest staying in degree mode; if you're taking Calculus or more advanced mathematics then I'd seriously suggest sticking with radian mode. Either way, go to your MODE screen and toggle it to the desired setting. ALSO, if you're graphing a trig function then you will want to be in radian mode.


Now...to try to answer your question:
A. You are either asking to find the ARCSECANT of -1.2.
OR
B. You are asking to find the SECANT of -1.2 radians.

A. TI-84 does not have a SECANT button (from what I remember); because the reciprocal trig functions aren't as important as sine, cosine, and tangent. This isn't bad news. All you need to do to find the arcsecant (aka the inverse secant) of a value is find the arccosine of that value [arccos(-1.2)] and find its reciprocal (ie, flip the number upside down: the reciprocal of 5 is one-fifth). Viola, you're done.

B. TI-84 only uses the three basic trig functions. Secant is the reciprocal of cosine. Therefore, in order to find the secant of -1.2 radians you need to be in Radian mode (see #2 above). From there, you just find the cosine of -1.2 and take that values reciprocal (ie, flip the number upside down: the reciprocal of 10 is point one) . Viola, you're done.


Math lesson: 1 Radian = 180 Degrees. Therefore, 1.2 Radians is roughly one-third of pi, therefore it is roughly one-third of 180 degrees; therefore -1.2 radians would be nearly -60 degrees (a very friendly angle measure).

I hope that helps If not, you should call Texas Instruments because they've got friendly people who are happy to assist anyone. Questions like this are right up their ally, advanced questions like the syntax of the poisson cumulative distribution function are not. So, you're fine. For in depth math help holler at www.THEMATHCHEETAH.com




In Short: Secant returns ratios and NOT degrees or radians. Secant is the reciprocal to cosine. Arcsecant WILL return degrees/radians. Your calculator can be set to either mode.


TEXAS INSTRUMENTS >>>>> all calculators ever made.

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1 Answer

My casio s/c fx83ES does not have an INV button. Can you help me


I depends on what you mean by INV.
On some Chinese (AUREX, Staples) calculators the second function key is marked as INV. If that is the key you have in mind, on Casios it is the [SHIFT] key. On Sharps it is marked as [2ndF]

If you have in mind the multiplicative inverse (the reciprocal) then your calculator has such a key and it is marked [x^-1]. It the key represented on the following table at the intersection of the 2nd column and the 9th line (RECIPROCAL)

dc4ae01.jpg

If you are thinking about the inverse of functions, then know that each function shares the same physical key as its inverse. For example to access the arcsine (the function inverse of sine) you press the [SHIFT] key before [SIN]. On the calculator you will notice that near the [SIN] key and to its left there is [SIN^-1].

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0.5=log Io/It find Io/It


Hello
A set a parentheses would sure help remove any ambiguities.
I assume your equation is 0.5 =log(lo/lt)
There is an equivalence

y=log(x) is equivalent to x=10^y

You can write
10^(0.5)=10^(log(lo/lt))
But 10^(log(x))=x, thus
10^(0.5)= lo/lt
and lo/lt=square root of 10
Here is a screen capture to convince you.

4380fcc.jpg

Hope it helps

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1 Answer

My log functions are wrong


Hello,
It would help to know what you are trying to do or at least in what way you answers are wrong. I will do my best to guess right.

Ex: if you enter log(25) it gives you 2*log(5) and if you enter log(5) it echoes the same thing. If that is waht you get, it is easy to fix.
Press the Main icon at the bottom of the screen to open the calculator run screen. Unfold the first Menu to the left of Edit. Press Settings (first submenu) Press the/arrow and select Setup item, then Basic Format. Under Common tab you have the different formats: folder, display, angle, and Advanced. Put a check mark in the box to the left of Decimal Calculation an press Set to save configuration.

The other possibility is that you actived the 2D keyboard which gives you access to the 2d Function templates. You use these to calculate the log in arbitrary bases. Functions on this keyboard have a dark rectangle. If that is the source of your problem, use the stylus to select the mth keyboard.
Hope it helps.

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TI-30xa Calculator Reciprocal Key


It does. For instance, to get the reciprocal of 4, enter the following sequence: 4 [1/x] (this last key to be found third row down, second black key in). The decimal 0.25 will appear as the result. Convert this, if you want, to the fraction 1/4 by pressing the yellow function key [2nd], then {F<>D] located bottom, far left. Hope that's what you wanted!

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