View Full Version : Law of Sines?

A friend of mine made this picture to illustrate the law of sines.

http://img27.photobucket.com/albums/v81/Krakkles/law_of_sines.jpg

I kinda see a pattern, but not completely...and I don't know how this knowledge would be useful.

It's not really. Sure, it shows what is going on, but I don't think I'd put that in a tutorial or anything.

EvBladeRunnervE

03-24-2004, 09:05 AM

and I don't know how this knowledge would be useful.

law of sines can be used to find the length of a side, given you know one other side's length and angle opposite to it, and know the angle of the side opposite to it(you probably gathered this). The uses are numerous, and include triangulation of an object(such as the moon).

linuxdude

03-24-2004, 09:48 AM

the theorem stateshttp://hyperphysics.phy-astr.gsu.edu/hbase/images/lsin.gif

what the hell is the point of this thread?? and, yes law of sines and cosines is very useful...how can you not see that?? ahhhhh

;)

XSquared

03-24-2004, 01:06 PM

Here's a sample application:

You're in engineering, and need to know the height of an object. You're standing 50 meters away from the base of the object, and when you measure from the ground to the top of the object, it is a 48 degree angle (from horizontal). You know that the object makes a 83 degree angle with the ground.

Hint: Draw a diagram to understand it better. I can't make up one right now.

Solution:

let d be the distance from you to the object

let h be the height of the object

let theta be the angle from the ground to the top

let alpha be the angle the object makes with the ground

let gamma be the other angle in the triangle

gamma = 180 - theta - alpha

= 49

sin gamma / d = sin theta / h

sin49 / 50 = sin48 / h

h = 50sin48 / sin49

h = 49.23 (approx)

XSquared

03-24-2004, 01:13 PM

Here's a diagram.

Leeman_s

03-24-2004, 05:29 PM

What's it useful for? It's useful so we can algebraically find values of sides and angles of trianges we wouldn't otherwise be able to find, without measuring ourself.

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