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Thread: Why doesn't Math.tan() work?
 08092011, 07:37 AM #1Member
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 08092011, 07:39 AM #2
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The trig methods take radians, not degrees. See the Math class for methods that convert degrees to radians.
kind regards,
JosLast edited by JosAH; 08092011 at 07:43 AM. Reason: duplicate word ...
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 08092011, 07:41 AM #3Member
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Ah! I've been searching google for "java tan bug" this whole time. Thanks!
 08092011, 07:49 AM #4
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Build a wall around Donald Trump; I'll pay for it.
 08092011, 07:54 AM #5Member
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Ok. Sorry to come back with another question but I'm pretty bad at math in general.
Java Code:angle = Math.atan(Math.toRadians(1)); System.out.println("angle: " + angle);
Prints angle: 0.017451520651465824
This works
Java Code:angle = Math.tan(Math.toRadians(45)); System.out.println("angle: " + angle);
 08092011, 07:58 AM #6
Read the API, don't guess around. In any case, why should the argument to atan(...) be in radians (or even degrees, for that matter)?
db
 08092011, 08:01 AM #7
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The tan( ... ) method takes a number in radians and returns a number without a dimension so the inverse of the method (atan) takes a number without a dimension and returns a number measured in radians; so make that snippet:
Java Code:angle = Math.toRadians(Math.atan(1));
kind regards,
JosBuild a wall around Donald Trump; I'll pay for it.
 08092011, 08:10 AM #8Member
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Ok. Again thank you. This saved me from an hour of hair pulling.
Read the API, don't guess around.
public static double atan(double a)
Returns the arc tangent of an angle, in the range of pi/2 through pi/2. Special cases:
If the argument is NaN, then the result is NaN.
If the argument is positive zero, then the result is positive zero; if the argument is negative zero, then the result is negative zero.
A result must be within 1 ulp of the correctly rounded result. Results must be semimonotonic.
Parameters:
a  the double value whose arc tangent is to be returned.
Returns:
the arc tangent of the argument.
 08092011, 08:24 AM #9
 08092011, 09:11 AM #10Member
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Certainly.
Java 2 Platform SE v1.3.1: Class Math
I think it may be an older API. I've been using the older api without issues thus far though.
 08092011, 09:20 AM #11
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Fun; that old API documentation is dead wrong; as I wrote (see above) the tan( ... ) method takes a number in radians and returns a dimensionless number. That atan( ... ) method works the other way around (as an inverse function should): it takes a dimensionless value and returns a number measured in radians. It's probably a copy/paste error ;)
kind regards,
JosBuild a wall around Donald Trump; I'll pay for it.
 08092011, 09:20 AM #12
Yikes!
You are 4 versions behind.
 08092011, 11:14 AM #13
A mathematical definition for tangent in Trigonometry:
The tangent of an angle is the opposite side over the adjacent side.
Therefore we can deduce that a tangent takes an angle and returns a unitless number.
Arctangent:
Arctangent is the inverse function of tangent.
Therefore the arctangent takes a unitless number and returns an angle.
In Java these angles have units of radians.If you aren't programming in Java, well that's just too bad.
I'd rather be using Ubuntu.
 08092011, 11:33 AM #14
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 04292012, 09:13 PM #15
Re: Why doesn't Math.tan() work?
Last edited by stchman; 04292012 at 09:15 PM.
If you aren't programming in Java, well that's just too bad.
I'd rather be using Ubuntu.
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