Subtented?

[Rustjive]

Can someone explain to me the idea of subtented angles? I've gotten responses that they're the angle opposite to the line...but this really becomes vague with any further thought. And to have angles subtented by the chord of a circle....

Responses please. If there is a more suitable forum for this, I will move it. I just came here because of the .999r problem from months back, and figured that perhaps this is the place for all the math junkies..

 

[The Dancing Peacock]

I'm not very technical, but what I remember subtend from is the description of a parsec. It is when 1 Astronomical Unit (distance from earth to sun ~ 93 million miles) subtends 1 degree. So you have to be far enough away so that 93 million miles only appears to be 1 degree across. I know more technical people are gonna pop in here with better explanations, so I'll leave mine at that

 

[thorin]

Here's a brief definition:

"To be opposite to and delimit: The side of a triangle subtends the opposite angle."

And I believe this is what The Dancing Peacock was talking about:

"One generally measures the position of a star against the background, then waits 6 months so that it will have its maximum shift. That makes a baseline of 2AU; the angle so measured will be twice the parallax. The distance to a star which exhibits a parallax p of 1 arc sec is called 1 parsec (pc, this is equivalent to about 3.26 light years). In general, d (pc) = 1/p (arc sec). Even the closest star to us (Proxima Centauri) has a smaller parallax than that. One arc sec is about the angle subtented by a nickel seen at a distance of 1 kilometer, so parallaxes are not easy to measure! The best we can do from the ground is about 100 pc, though new techniques are improving that. From space (without atmospheric turbulence) we can measure stars to several hundred pc, and there are experiments being designed that might extend the reach of "trigonometric parallax" to several thousand pc, putting much of the Galaxy finally within the reach of direct measurement. "

Thorin