X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from host.roblinphoto.com ([72.52.218.78] verified) by logan.com (CommuniGate Pro SMTP 5.2c4) with ESMTPS id 2642154 for flyrotary@lancaironline.net; Sat, 12 Jan 2008 10:56:20 -0500 Received-SPF: pass receiver=logan.com; client-ip=72.52.218.78; envelope-from=bob@bob-white.com Received: from c-68-35-160-229.hsd1.nm.comcast.net ([68.35.160.229]:54719 helo=quail) by host.roblinphoto.com with esmtpa (Exim 4.68) (envelope-from ) id 1JDiNe-0001s2-Ql for flyrotary@lancaironline.net; Sat, 12 Jan 2008 10:34:43 -0500 Date: Sat, 12 Jan 2008 08:54:32 -0700 From: Bob White To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Re: Angles Message-Id: <20080112085432.7d635e55.bob@bob-white.com> In-Reply-To: References: X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.0; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - host.roblinphoto.com X-AntiAbuse: Original Domain - lancaironline.net X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - bob-white.com 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 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 > > *To:* Rotary motors in aircraft > > *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 > > > > > > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html -- N93BD - Rotary Powered BD-4 - http://www.bob-white.com 3.8 Hours Total Time and holding Cables for your rotary installation - http://roblinstores.com/cables/