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#1
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Trig Function seems odd.
G'day there One & All,
I've used XL to try to solve a simple trig problem, but the results have thrown me somewhat. I've no doubt the fault is mine, but I can see what's wrong. The problem is to determine timber thicknesses along a right angled taper: +--5--+--5--+--5--+--5--+--5--+ | 5 | + I want to determine the distance from each '+' to the hypotenuse. It should be simple enough. I use the formula '=1/TAN(5/25)' to determine the angle, (4.933154876) and then use '=A11*TAN(RADIANS($B $8))'. [$B$8 is where the angle is stored. A11:A15 holds the series 5,10,15,20,25]. I get the series 0.4, 0.9, 1.3, 1.7, 2.2 as a result. I know this is incorrect since the problem itself gives the final member as 5. I think I may have neglected a conversion between degrees & radians somewhere, but when I try to resolve it that way the results are more ridiculous than what I have already. Can anyone there see what I've done wrong? The web searches I've done so far either confirm the formulae as correct, or explain the functions in such a complex manner that I don't understand what's going on (you can probably guess that my high school trig knowledge is just a trifle rusty). Thanks for listening, Ken McLennan Qld, Australia |
#2
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Trig Function seems odd.
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#3
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Trig Function seems odd.
This problem does not require Trig at all... you can do it with simple
proportions. Since this sounds like homework, I'll let you set up the solution on your own. However, draw the hypotenuse, and then drop the perpendiculars from the + signs down to the hypotenuse. The ratio between any two sides (think the two sides that are not hypotenuses) in each smaller triangle formed by dropping the perpendiculars is equal to the ratio between the same two sides in the large triangle. Since you know two sides in the large triangle and you know one side those sides in each of the smaller triangles, you can calculate the missing side. Rick "Ken McLennan" wrote in message ... G'day there One & All, I've used XL to try to solve a simple trig problem, but the results have thrown me somewhat. I've no doubt the fault is mine, but I can see what's wrong. The problem is to determine timber thicknesses along a right angled taper: +--5--+--5--+--5--+--5--+--5--+ | 5 | + I want to determine the distance from each '+' to the hypotenuse. It should be simple enough. I use the formula '=1/TAN(5/25)' to determine the angle, (4.933154876) and then use '=A11*TAN(RADIANS($B $8))'. [$B$8 is where the angle is stored. A11:A15 holds the series 5,10,15,20,25]. I get the series 0.4, 0.9, 1.3, 1.7, 2.2 as a result. I know this is incorrect since the problem itself gives the final member as 5. I think I may have neglected a conversion between degrees & radians somewhere, but when I try to resolve it that way the results are more ridiculous than what I have already. Can anyone there see what I've done wrong? The web searches I've done so far either confirm the formulae as correct, or explain the functions in such a complex manner that I don't understand what's going on (you can probably guess that my high school trig knowledge is just a trifle rusty). Thanks for listening, Ken McLennan Qld, Australia |
#4
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Trig Function seems odd.
It is if you copy it and drop it into Notepad (where the font is a
fixed-width one instead of the proportional one used by default in newsreaders). Rick "Ken McLennan" wrote in message ... In article , says... The problem is to determine timber thicknesses along a right angled taper: +--5--+--5--+--5--+--5--+--5--+ | 5 | + I've just noticed in my post that the diagram is a bit askew. It's supposed to be a simple right triangle. See ya, Ken McLennan Qld, Australia |
#5
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Trig Function seems odd.
G'day there Rick,
It is if you copy it and drop it into Notepad (where the font is a fixed-width one instead of the proportional one used by default in newsreaders). You know, even after several years of using Gravity, I never even noticed it used a proportional font!! Kinda says something about my powers of observation! See ya Thanks for your help Ken |
#6
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Trig Function seems odd.
G'day there Rick,
This problem does not require Trig at all... you can do it with simple proportions. Since this sounds like homework, I'll let you set up the solution on your own. Chuckle!!! If I was still young enough to be doing school homework I'd probably be young enough to remember my maths classes <g. However, draw the hypotenuse, and then drop the perpendiculars from the + signs down to the hypotenuse. The ratio between any two sides (think the two sides that are not hypotenuses) in each smaller triangle formed by dropping the perpendiculars is equal to the ratio between the same two sides in the large triangle. Since you know two sides in the large triangle and you know one side those sides in each of the smaller triangles, you can calculate the missing side. Aaaahhh yes... our old friend Pythagorus. I think he took sick and died a few years back. It's rather obvious when you explain it to me in one syllable words :) You're quite right of course, and just as I was reading your post I realised that it's also a simple matter of proportion - each 5 units is 20% of the adjacent side and so the opposite side can be divided into 20% sections to determine the results. I think the real problem was that when I tried to be smart and used XL I couldn't get it to work right and that became the problem I concentrated on; my triangles became a side issue. So, I can now easily determine the length of the sides, but why is my spreadsheet giving incorrect results? What have I gotten wrong there? See ya Thanks for your reply. Ken McLennan Qld, Australia |
#7
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Trig Function seems odd.
=1/TAN(5/25) doesn't give an angle, but =ATAN(5/25) does
And having calculated the angle that way (already in radians), you don't need the RADIANS function before using that in the TAN function. -- David Biddulph "Ken McLennan" wrote in message ... G'day there One & All, I've used XL to try to solve a simple trig problem, but the results have thrown me somewhat. I've no doubt the fault is mine, but I can see what's wrong. The problem is to determine timber thicknesses along a right angled taper: +--5--+--5--+--5--+--5--+--5--+ | 5 | + I want to determine the distance from each '+' to the hypotenuse. It should be simple enough. I use the formula '=1/TAN(5/25)' to determine the angle, (4.933154876) and then use '=A11*TAN(RADIANS($B $8))'. [$B$8 is where the angle is stored. A11:A15 holds the series 5,10,15,20,25]. I get the series 0.4, 0.9, 1.3, 1.7, 2.2 as a result. I know this is incorrect since the problem itself gives the final member as 5. I think I may have neglected a conversion between degrees & radians somewhere, but when I try to resolve it that way the results are more ridiculous than what I have already. Can anyone there see what I've done wrong? The web searches I've done so far either confirm the formulae as correct, or explain the functions in such a complex manner that I don't understand what's going on (you can probably guess that my high school trig knowledge is just a trifle rusty). Thanks for listening, Ken McLennan Qld, Australia |
#8
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Trig Function seems odd.
G'day there David,
=1/TAN(5/25) doesn't give an angle, but =ATAN(5/25) does And having calculated the angle that way (already in radians), you don't need the RADIANS function before using that in the TAN function. AHA!!!! It's so much easier when you know what you're doing! Thanks very much for that. I thought that ATAN was an Arctangent and had some other relationship to the angle and that I needed the inverse of the tangent. Oh well. Maybe I should have tried to remember my school stuff. Or learned it to begin with :) I've changed the formulae and all is now well with the world. However I think it would be much better if Microsoft built a spreadsheet program that just knew what I wanted and gave me the answers without me having to accurately formulate the questions :) Thanks once again for your help. Ken McLennan Qld, Australia. |
#9
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Trig Function seems odd.
ATAN is indeed the arctangent, and that's what you were trying to calculate.
I agree with your point that the difficulty is with knowing what question to ask, rather than in getting Excel to provide the answer. Perhaps your thought of using the inverse of the tangent is a consequence of being in the antipodes? :-) -- David Biddulph "Ken McLennan" wrote in message ... G'day there David, AHA!!!! It's so much easier when you know what you're doing! Thanks very much for that. I thought that ATAN was an Arctangent and had some other relationship to the angle and that I needed the inverse of the tangent. Oh well. Maybe I should have tried to remember my school stuff. Or learned it to begin with :) I've changed the formulae and all is now well with the world. However I think it would be much better if Microsoft built a spreadsheet program that just knew what I wanted and gave me the answers without me having to accurately formulate the questions :) Thanks once again for your help. Ken McLennan Qld, Australia. =1/TAN(5/25) doesn't give an angle, but =ATAN(5/25) does And having calculated the angle that way (already in radians), you don't need the RADIANS function before using that in the TAN function. |
#10
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Trig Function seems odd.
G'day there David,
ATAN is indeed the arctangent, and that's what you were trying to calculate. Gotta get back to the books I s'pose. Or just blunder on in ignorance. The latter has served me OK for the last 30 years or so :) I agree with your point that the difficulty is with knowing what question to ask, rather than in getting Excel to provide the answer. As they say "A little knowledge is a dangerous thing", and my knowledge of trigonometry is quite little. Perhaps your thought of using the inverse of the tangent is a consequence of being in the antipodes? :-) Hey!! There's an idea. I hadn't thought of that. After all, the sun does go anticlockwise down here. Widdershins instead of deosil <g. See ya, Thanks again, Ken |
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