I'm trying to convert the following javascript to java

var lat2 = Math.asin( Math.sin(lat1)*Math.cos(d/R) + 
          Math.cos(lat1)*Math.sin(d/R)*Math.cos(brng) );
var lon2 = lon1 + Math.atan2(Math.sin(brng)*Math.sin(d/R)*Math.cos(lat1), 
                 Math.cos(d/R)-Math.sin(lat1)*Math.sin(lat2));

it's all fairly simple except I'm unsure what the ma after cos(lat1) does? I read that in javascript it is used to assign the value after the a to a variable while still evaluating the first expression, although in the above code the expression before the ma is not stored?

Any help on converting this to java or understanding what the ma does?

The original maths formula also has a ma

φ2 = asin( sin(φ1)*cos(d/R) + cos(φ1)*sin(d/R)*cos(θ) )
 λ2 = λ1 + atan2( sin(θ)*sin(d/R)*cos(φ1), cos(d/R)−sin(φ1)*sin(φ2) )

I'm trying to convert the following javascript to java

var lat2 = Math.asin( Math.sin(lat1)*Math.cos(d/R) + 
          Math.cos(lat1)*Math.sin(d/R)*Math.cos(brng) );
var lon2 = lon1 + Math.atan2(Math.sin(brng)*Math.sin(d/R)*Math.cos(lat1), 
                 Math.cos(d/R)-Math.sin(lat1)*Math.sin(lat2));

it's all fairly simple except I'm unsure what the ma after cos(lat1) does? I read that in javascript it is used to assign the value after the a to a variable while still evaluating the first expression, although in the above code the expression before the ma is not stored?

Any help on converting this to java or understanding what the ma does?

The original maths formula also has a ma

φ2 = asin( sin(φ1)*cos(d/R) + cos(φ1)*sin(d/R)*cos(θ) )
 λ2 = λ1 + atan2( sin(θ)*sin(d/R)*cos(φ1), cos(d/R)−sin(φ1)*sin(φ2) )

• java
• javascript
• math

Share Improve this question Follow edited Jan 14, 2013 at 14:12 Danilo Valente 11.4k88 gold badges5454 silver badges7070 bronze badges asked Jan 14, 2013 at 14:11 drunkmonkeydrunkmonkey 1,19111 gold badge1717 silver badges2727 bronze badges

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3 Answers 3

Sorted by: Reset to default 11

It's not an operator, it's simply separating the two arguments to atan2. It's exactly the same in Java.

(Recall that atan2 takes the x and y ponents separately, in order to resolve rotational ambiguity.)

Math.atan2 method accepts two arguments. Comma simply separates it.

Math.atan2(y, x)

Returns the arctangent of the quotient of its arguments.

Reference:

• https://developer.mozilla/en-US/docs/JavaScript/Reference/Global_Objects/Math/atan2

The only change required is to give the variables a type.

double lat2 = Math.asin(Math.sin(lat1) * Math.cos(d / R) +
        Math.cos(lat1) * Math.sin(d / R) * Math.cos(brng));
double lon2 = lon1 + Math.atan2(Math.sin(brng) * Math.sin(d / R) * Math.cos(lat1),
        Math.cos(d / R) - Math.sin(lat1) * Math.sin(lat2));