Trigonometry maths help

yoda · 16 Oct 2008 at 18:05

it's been 13 years since i last used trig (at school) and my memory isn't that wonderfull...

basically, i' trying to work out direction of travel when i know my curent long and lat position and i know the long and lat of where i'm trying to go...

the formula i found sofar is...

TAN a = longitude diference / latitude diference

so, for example... if the longitude diference is 50 and latitude diference is also 50 then the tangent of the angle is 1...

How do i then work out what the angle is from the tangent? :confused:

Thanks

touch · 16 Oct 2008 at 18:08

yoda said:
if the longitude diference is 50 and latitude diference is also 50

45 degrees?

(you need to use the [tan^-1] button on your calculator i think)

Azagoth · 16 Oct 2008 at 18:11

yoda · 16 Oct 2008 at 18:12

well done... i allready knew that... i'm after how to convert it... whats the formula to work it out...

I picked 50 by 50 coz it's odvious the answer should be 45...

Vonhelmet · 16 Oct 2008 at 19:09

yoda said:
well done... i allready knew that... i'm after how to convert it... whats the formula to work it out...

You use inverse tan, like you got told. :confused:

DaveF · 16 Oct 2008 at 21:25

Sorry, but this isn't right.

To give an extreme example, what direction to you need to go from (90, 80) to (-90, 80)? The arctan(long_difference/lat_difference) implies you should go due East, but you should actually go due North.

DaveF · 16 Oct 2008 at 21:33

This might help...

http://www.movable-type.co.uk/scripts/latlong.html

G-MAN2004 · 16 Oct 2008 at 21:35

Azagoth said:
42

Every maths thread..

apeZ · 16 Oct 2008 at 22:35

G-MAN2004 said:
Every maths thread..

Sadly never get the joke

David91 · 16 Oct 2008 at 22:36

watch The Hitchhiker's Guide to the Galaxy

PaulLambeth · 16 Oct 2008 at 22:36

apeZ said:
Sadly never get the joke

The answer to life, the universe and everything?

Grrrrr · 16 Oct 2008 at 22:36

G-MAN2004 said:
Every maths thread..

And it's not been funny even once

David91 · 16 Oct 2008 at 22:36

/Ignore

Vonhelmet · 16 Oct 2008 at 23:03

DaveF said:
Sorry, but this isn't right.

To give an extreme example, what direction to you need to go from (90, 80) to (-90, 80)? The arctan(long_difference/lat_difference) implies you should go due East, but you should actually go due North.

It's right if the angle in question is a bearing from North... I think.

BigglesPiP · 16 Oct 2008 at 23:10

The squr of the hippopotamus is equal to the sum of the squrs of the other two sides.

SoapSurgeon · 16 Oct 2008 at 23:11

at the risk of sounding like a geek...

Aren't lat/long coordinates spherical and not Cartesian? Your trig answer might not be 100% accurate

Vonhelmet · 16 Oct 2008 at 23:13

SoapSurgeon said:
at the risk of sounding like a geek...

Dude, you're in a maths thread on a computer forum. I'd be more worried about sounding like you weren't a geek.

DaveF · 17 Oct 2008 at 08:40

SoapSurgeon said:
Aren't lat/long coordinates spherical and not Cartesian?

Yes. See posts #6 and #7.

<is this mike on...?>

SoapSurgeon · 17 Oct 2008 at 09:47

DaveF said:
Yes. See posts #6 and #7.

<is this mike on...?>

I didn't realise it was customary to read the thread before posting a reply, especially not an external link!

Oh, and by the way, it's spelt mic.

<*tap* *tap* Is this spell checker on?>

Azagoth · 17 Oct 2008 at 16:56

G-MAN2004 said:
Every maths thread..

Yeah, but one of these times it's got to be right.