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In addition, "vertical" length and "horizontal" length sort of narrows
it down to a right triangle. Another interesting rule of thumb: For small angles the sine, tangent,
and angle are all the same. (The angle is measured in radians rather
than degrees. There are 2*pi radians in 360 degrees.) The smaller the
angle the more accurate the rule of thumb.
For Georges problem:
tangent is 3/30 = .1
sine is 3/30.1496 = .09950 (denominator from Pythagorean theorem)
angle in degrees is 5.71059 (from the arc tangent)
so in radians it is 2*pi (5.71059/360) = .099669
and the difference between them is less than 0.5 %.
Bob W.
On Sat, 12 Jan 2008 07:25:53 -0700
Dale Rogers <dale.r@cox.net> wrote:
But Joe, any triangle can be divided into two right triangles.
Dale R.
Joe Ewen wrote:
> For those who may use this formula, this formula will only work on a > right triangle. Please correct me if I am wrong.
> Joe
> > >
> ----- Original Message -----
> *From:* Ed Anderson <mailto:eanderson@carolina.rr.com>
> *To:* Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
> *Sent:* Saturday, January 12, 2008 8:30 AM
> *Subject:* [FlyRotary] Re: Angles
>
> Hi George,
> > Several folks have responded to your question concerning angles,
> for what it is worth I also got 5.729 degrees.
> > There are a couple of formulas you can use. One common approach
> is to use
> ArcSin, but unless you have a convenient ArcSin function available
> that can be problematic.
> > So instead I like to use this one for y/r (y being the vertical
> length of your angle and r the horizontal length) Degrees = y/r
> * 180/pi = 3/30*180/3.1456 = 5.729 deg. This way you don't
> need a table/function of ArcSin.
> > Ed
> >
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