Why are sine and cos not coming correctly on my calculator?

Question

I know that sin 30 is equal to .866 but on my calculator I keep getting -0.98803. Why is that? And if I try using sin-1 then I get error 1 Quit 2 Goto on my calculator. My model is Texas Instruments TI-83 Plus. And I also get 0.154251 if I try doing cos 30 instead of 0.5. Am I doing something wrong? Do I need to change batteries or buy a new calculator? I have a test on Tuesday and I need to practice. Thanks.

Answer 1

As others have said, your calculator is set to radians instead of degrees. To change it on a TI-83+, hit the MODE button and scroll down to the RADIANS/DEGREES option, highlight degrees and hit enter.

Answer 2

You don't need a new calculator.

Your calculator is giving you the answer assuming that you are feeding it radians.

In other words it has correctly given you the value of sin ( 30 radians).

NOT sin ( 30 deg)

On most calculators there is a button often marked D/G/R which you can use to switch between degrees ( 360 makes one circle) Rads ( 100 rads makes one circle) or radians ( 2 PI() radians makes one circle)



Sin^-1 is only valid if the input is between -1 and 1

It is used to find the angle that would create the sin that you specify.

Again unless you have your calculator set it will give you the answer in radians, not in degrees.

Answer 3

My calculator is giving me that sin 30 is 0.5 and cos 30 is .866 not the other way around, but your problem is that your calculator is set to radians not degrees, I'm not 100% sure for TI (I have a casio) but get to set up (On mine that's shift + menu) and just change the angle option to degrees.

Answer 4

Hit [Mode] and change from Radian mode to Degree mode. Also, sin(30°) is 0.5, while cos(30°) ≈ .866.

Answer 5

sin 30 is 0.5. Make sure that your calculator is set to degrees and not radians or grads.

Answer 6

I don't really know how to change it for your model, but you probably have it set to radians instead of degrees. You need to figure out how to change it back.

Answer 7

get it checked with someone who deals in this.