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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Posted on Jan 02, 2017

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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**

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

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

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...

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.

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

Hi ssmith63,

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

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.

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

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

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

If you are entering your numbers from sin, cos, and tan as degrees and you are in radians, your answers will be off. Same goes for if you are inputting radians while in degree mode. Hope this helps

If you are entering your numbers from sin, cos, and tan as degrees and you are in radians, your answers will be off. Same goes for if you are inputting radians while in degree mode. Hope this helps

Dec 26, 2010 | Texas Instruments TI-83 Plus Calculator

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!

Jun 03, 2010 | Texas Instruments TI-83 Plus Calculator

Hello,

That habit of TI, Casio, and Sharp to label the inverse trigonometric functions with the -1 superscript can cause confusions.

Hope it helps

That habit of TI, Casio, and Sharp to label the inverse trigonometric functions with the -1 superscript can cause confusions.

- The inverse trigonometric functions arcosine, arcsine, and arctangent (labeled by manufacturers as cos^-1, sin^-1, and tan^-1) should not be confused with the other trigonometric functions known as secant(x) =1/cos(x), cosecant(x)=1/sin(x) and cotangent(x) = 1/tan(x).
- To avoid errors in the use of the inverse trigonometric functions, one must be careful and set the angle unit to the one required by the problem at hand (degrees, or radians)
- To make the trigonometric functions really functions, their range is restricted.
- In this calculator arcosine (x) gives results between 0 and 180 degrees (if angle MODE is Degree) or between 0 and Pi radians (if angle MODE is Radian).
- The range of results for arcsine(x) and arctangent(x) is between -90 degrees and +90 degrees (if angle MODE Degree) or -Pi/2 and Pi/2 (if angle MODE is Radian)

Hope it helps

Nov 06, 2009 | Texas Instruments TI-83 Plus Calculator

Hello,

It may be due to the angle unit used. You can have angles in degrees, in radians, and in grads. You should set the default angle unit to waht you problem calls for.

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.

Hope it helps.

It may be due to the angle unit used. You can have angles in degrees, in radians, and in grads. You should set the default angle unit to waht you problem calls for.

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.

Hope it helps.

Sep 16, 2009 | Casio FX-115ES Scientific Calculator

Hello,

To avoid problems,set your angle unit to radians by default. Press [MODE]. If**Radian ** is highlighted (text on black background), it is indeed the default mode. If **Degreee **is highlighted, scroll dowm to the line and use the left arrow to select Radian and press ENTER. Radian will start blinking.

Any number you feed a function that acts on angles (sin, cos, tan) will be considered in radians. Any result that comes out of the inverse trigonometric functions (arcsin, arccos, arctan) is in radian. The angle coming from a conversion from cartesian coordinates to polar coordinates is in radian.

You have a simple way to convert the value from radians to degrees because 1 rad=180/pi. Store this value in a variable [STO->] D

**180/[2nd][PI] [STO->] D**

Since the last result is always stored in [Ans] all you have to do is to multiply by D:**[Ans][x][ALPHA]D converts results in degrees.**

Hope it helps

To avoid problems,set your angle unit to radians by default. Press [MODE]. If

Any number you feed a function that acts on angles (sin, cos, tan) will be considered in radians. Any result that comes out of the inverse trigonometric functions (arcsin, arccos, arctan) is in radian. The angle coming from a conversion from cartesian coordinates to polar coordinates is in radian.

You have a simple way to convert the value from radians to degrees because 1 rad=180/pi. Store this value in a variable [STO->] D

Since the last result is always stored in [Ans] all you have to do is to multiply by D:

Hope it helps

Sep 14, 2009 | Texas Instruments TI-83 Plus Calculator

Your calculator is set in radians. Press mode key. Arrow down to 3rd line. Highlight degree and press enter. Your calculator is now in degrees, not radians. To get out of the mode screen and back to home screen, press 2nd and then mode.

Aug 05, 2009 | Texas Instruments TI-84 Plus Calculator

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