Thread: Confusion with Math.toDegrees() and Math.toRadians(). Please help.

Dear administrators and members,

A greeting of peace.

I hope everyone is in good health upon reading this thread.

I am currently working on a simple program that uses trigonometric laws like sine laws. I first try to write this simple codes first:

double angle = 60;
System.out.println( Math.sin(Math.toDegrees(angle) );

Then the output is: 0.7475(something)

I wonder why the output is 0.7475(something)? BUT, when I tried pressing sin 60 on my scientific calculator (in degrees mode as usual) the answer is 0.8660(something).

Then later, I tried to use toRadians() method in Math class:

double angle = 60;
System.out.println( Math.sin(Math.toRadians(angle) );

Then that is the time I got the 0.8660 (something) answer.

I am just a little confused. My scientific calculator is in degrees mode, that is why I am expecting the same result if I will use the toDegrees() method, but why it did not?

Please enlighten me. Did I miss something?


Respectfully Yours,

MarkSquall

Hi,

for Math.sin(doulbe a), a is an angle, in radians (pls refer to in API document), that's why sin(Math.toRadians(angle)) works.

one more thing, following words are from API document, FYI.
about toDegrees, "The conversion from radians to degrees is generally inexact; users should not expect cos(toRadians(90.0)) to exactly equal 0.0. "

Dear Ms. ivy,

I already read the Java API documentation, and it's a great help for some useful definition. BUT, I just wondered why toRadians() is the one gave me the correct answer (as the one in my scientific calculator) than toDegrees() .

Is it not if I press sin 60 in my scientific calculator, 60 is already (or "converted") in degrees (since my calculator is in DEG mode)?

But anyway, a million thank you and more power.

Warm regards,

MarkSquall