Question about Texas Instruments TI-83 Plus Calculator

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Radian mode does not work properly

I keep getting wrong answers with the radians mode on. What i typed in was cos(20π + (π/2)) and I get a weird answer (-1E-13) when i know the answer should be zero because i did it on another calculater and that's what i got. Please help me, i have no idea what could be wrong because with other specific things (sin( 20π + (π/2)) for example) ive typed in it does give the right answer, but i don't know why with the other one it doesn't.
Thank you,
Maria

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-1E-13 is a very small number. When doing this kind of a problem you can regard 1E-13 as 0.

Remember that pi is an irrational number. It is only estimated on your calculator. I just played around with a TI-83 and found the following answers:

cos(pi/2) = 0
cos(2*pi + pi/2) = 0
cos(4*pi + pi/2) = 1E-13
cos(20*pi + pi/2) = -1E-13

As you know, that correct answer to each of these is 0. The calculator gives non-zero answers because some very small errors are accumulating. There is nothing wrong with your calculator.

Posted on Nov 20, 2007

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2 Answers

My calculator is not computing sin^-1 or cos^-1 correctly, I put sin^-1(0.184) in and it came out with 10.60283... when I should be getting 1.39. HALP?


When the angle unit is in radians
sin^-1(0.184)=0.1850543940 radians
When angle unit is in degrees
sin^-1(0.185)=10.60283581
Your calculator is calculating the functions correctly)
In the following screen captures the sine of the values is calculated with the unit specified inside the formula (degree symbol and radian symbol are inserted to show you the unit). In the last calculation the value of the sine is practically 0.184
Remember that when angle is in radians, for very small angles (less than 10 degrees), sin(x) and tan (x) are about equal to the value of the angle in radians

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Mar 25, 2014 | Casio FX-115ES Scientific Calculator

1 Answer

Cot(x) = -0.6


Let's start with a little background.

The cot(x) is also known as the cotangent(x) and it equals 1/tan(x) which equals cos(x)/sin(x). I'm showing these formulas because your calculator may not have a cot button but it will probably have buttons for tan, cos, and sin.

Your calculator may also have buttons for tan-1, cos-1 and sin-1. These are the inverse functions for tan, cos, and sin. If you enter a number and then push the tan-1 button, the result is the angle whose tangent is the entered number. For example, it you enter 1 and push the tan-1 button the answer will be 45 deg because tan (45 deg) = 1.

Now let's look at the problem, cot(x) = -0.6.
The first thing we need to know is do you want the answer in degrees or radians? Your calculator will have both modes. The default mode when you first turn it on is probably degrees. If this problem is in radians you will need to change the mode of your calculator over to radians before we start.

If cot(x) = -0.6, then tan(x) = 1/-0.6 from the formula I showed in the background section.

This means tan(x) = -1.6666666...

Now we just enter -1.66666667 and hit the tan-1 button to get the answer.

If we're operating in radians the answer is -1.0307 radians.
If we're operating in degrees the answer is -59.036 deg.

I hope this helps you out.

Dec 06, 2011 | SoftMath Algebrator - Algebra Homework...

1 Answer

Any sin, cos, or tan function problem always gives the incorrect answer. I can use my TI 55 that is 30 years old and get the correct answer, but my son's TI84 plus silver edition is incapable of giving the...


Make sure you have the proper angular mode set. The TI-84 can work with degrees or radians.

Press MODE to bring up the mode screen. Use the arrow keys to highlight either "Radian" or "Degree" on the third line and press ENTER. Press 2ND [QUIT] to exit the mode screen.

If this doesn't do it, please reply to this post giving an example of a calculation and the answer you're getting from the calculator.

Feb 03, 2011 | Texas Instruments TI-84 Plus Calculator

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How do i enter this question on a ti 89? 5 sin(2 pi 2000 t +60 degrees) does anybody know i would appreciate it.


Hi ssmith63,
Put the calculator in radian angle mode. The top answer is in AUTO mode and, The bottom is in Approx mode.

oneplusgh_47.jpg
I converted 60 degrees into pi/3 radian which equals 1.0472 radians. I figured 5 significant digits was good enough since, you only went 4. If you have any question just post them and, I'll respond quickly.

Jan 15, 2011 | Texas Instruments TI-89 Calculator

1 Answer

Sin, cos, and tan do not seem to work properly.


Press "Mode" Check to see if you are in radian mode or degree mode (one of the top categories)
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1 Answer

Whenever i put in sin or cos or tan on my calculator the wrong answer comes up, how do i fix this?


Most likely you do have the calculator in radians (or if you are working in radians, you have it in degrees). Press the mode button, move cruser down to "radians degrees" highlight degrees. and press "2nd quit". things sould be better!

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1 Answer

I am getting the wrong answers with the tan -1 function


Hello,
That habit of TI, Casio, and Sharp to label the inverse trigonometric functions with the -1 superscript can cause confusions.
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  3. To make the trigonometric functions really functions, their range is restricted.
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2 Answers

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Hello,
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To set degree as default SHIFT MODE 3
To set radians as default SHIFT MODE 4
To set grads as default SHIFT MODE 5

The values of angles calculated by the inverse trigonometric functions are in the default unit that is set . This may be the source of the wrong answers that you get.

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1 Answer

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Hello,
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