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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Fri Jul 08, 2011 12:50 am Post subject: Need dimensions for a 16:9 screen |
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Hey everyone, need a second screen for working on my projector. I need to know the dimensions for a 80" diagonal 16:9 screen. I would appreciate any help! 
Thanks!
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Fri Jul 08, 2011 3:02 am Post subject: |
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Pythagorean theorem: a^2 + b^2 = c^2. a is screen width, b is screen height, c is diagonal.
For the basic unscaled 16:9 numbers, that's 16^2 + 9^2 = c^2, c = sqrt(16^2 + 9^2) = 18.36.
Now you want to scale 16:9 with an 18.36 diagonal up to an 80" diagonal, so your multiplier is 80 / 18.36 = 4.36.
a = 16 * 4.36 = 69.72", b = 9 * 4.36 = 39.24". The diagonal is sqrt(69.72^2 + 39.24^2) = 80.0041".
If you want to round it off, a 70" x 40" screen gives you just about 80" diagonal -- sqrt(70^2 + 40^2) = 80.62" to be exact.
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Fri Jul 08, 2011 3:11 am Post subject: |
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sweet, Ill be sure to remember this, its very useful  Thanks Gary!
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Fri Jul 08, 2011 3:20 am Post subject: |
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I knew there'd be math in this thread.
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Fri Jul 08, 2011 5:50 am Post subject: |
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<<<------ Fully admit I didn't know how to calculate the dimensions for the screen :-\
Math to the rescue!
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Fri Jul 08, 2011 6:04 am Post subject: |
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Good ol' Pythagoras
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dvh99
Joined: 25 Dec 2009
Posts: 2158
Location: nederland
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| Posted: Fri Jul 08, 2011 9:05 am Post subject: |
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what i don`t understand is that even the ancient greeks (pythagoras, euclides) had great math skills and they still are in great debt now.
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marquee 9500ultra HD10L moome hdmi1.3 v3+ some mods.
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Tom.W
Joined: 09 Mar 2006
Posts: 6635
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Fri Jul 08, 2011 3:17 pm Post subject: |
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| dvh99 wrote: | | what i don`t understand is that even the ancient greeks (pythagoras, euclides) had great math skills and they still are in great debt now. |
No, they're dead now.  Their descendents seem to be a bit more math challenged.
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Jeremy112
Joined: 28 Sep 2006
Posts: 2649
Location: Fond du Lac, WI
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| Posted: Fri Jul 08, 2011 5:00 pm Post subject: |
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Screen is getting made today, will have it by 6:30PM my time, And by screen I mean the peice thats used to actually view the projected image, not the frame/border etc..
Just need it so I can finish setting up my new tubes!
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WanMan
Joined: 19 Mar 2006
Posts: 10270
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| Posted: Fri Jul 08, 2011 5:06 pm Post subject: |
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Jeez, no one could simply use Sine and Cosine (and Tangent's Inverse)? The angle is 29.36º. Height = Sin(29.36º), Width = Cos( 29.36º).
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Fri Jul 08, 2011 5:11 pm Post subject: |
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You'd have to use arctan(9/16) to figure the 29.36° angle. Then sin(29.36°) gives you the height of a screen with a unit diagonal, so remember to multiply 80" * sin(29.36°) = 39.22", etc.
But whaddaya you got against Pythagoras? Most people are more comfortable with square roots than they are sines, cosines, and arctangents.
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416ray4538
Joined: 14 Jul 2009
Posts: 517
Location: near Toronto Ont
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| Posted: Sat Apr 26, 2014 4:09 pm Post subject: |
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Speaking of Pythagoras, anyone know what the hell he was working on to come up with the 81:80 comma. The only place I know of where it shows up is in tuning with 12 semitones to the octave. It's the error on the fifths. 
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