No quite PLC talk: Re:Formula for LCD Screen Size?

Anibal Hernandez

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Join Date
Aug 2003
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Gentleman:



No quite PLC talk: Re:Formula for LCD Screen Size?





Does anyone knows the formula for determining the width and the height dimensions of an LCD Flat screen computer monitor provided you know the Diagonal and the Aspect Ratio dimensions?



Example:



21.3” LCD Screen

With an Aspect Ratio of 16:9

What are the width and the height dimensions?





Thanks all
 
A matter of angles

Like the link above will lead you to, a right triangle with a hypotenuse of 21.3" will have a opposite and adjacent side with a 90 deg. angle at the intersection of the opposite and adjacent sides. There are two remaining angles in the shape and one can be 60 and the other 30 or both be 45 degrees and still add up to the required 180 degrees for the total angles. The 60/30/90 triangle produces a rectangle when doubled and the 45/45/90 produce a square when the area is doubled. Now, most monitors have rectangle shape so the rest is just a matter of algebra. Easiest way to explain aspect ratio is to say that it means the ratio between the width of the picture and the height of the picture.
 
The aspect ratio of 16:9 (1.78) is equal to the tangent of the angle opposite the longer side. The inverse of the aspect ratio (9:16 = .5625) is equal to the tangent of the angle opposite the shorter side.

If you know the tangent of an angle, you can calculate the angle. Once you know the angle, you can calculate its sine or its cosine. The length of the side opposite an angle is equal to the hypotenuse times the sine. The length of the side adjacent to an an angle is equal to the hypotenuse times the cosine.
 
SOHCAHTOA - I resesrve my comments about engineers .
Either didn't go to school in PR or were to smashed for simple maths. Either way - WAKE UP.
 
Fred

Dont know if I am an engineer BUT the Navy taught me
S suzy
C can
T tell

O oscar
H has
A a
H ha**
O o*
A always

Does yours have a ditty that everyone ALWAYS remembers ??

Dan Bentler
 
Ah - but this is also easily solvable without resorting to trigonometry with all the SOHCAHTOA stuff. The diagonal and aspect ratio is enough. Want me to show the math?
 
Pythagoras does indeed rule

16 * X = Long Side
9 * X = Short Side
21.3 = Hypotenuse

Square Root( Long Side ^2 + Short Side ^2) = Hypotenuse

Square Root( (16 * X)^2 + (9 * X)^2)) = 21.3
Square Root( (256 * X^2) + (81 * X^2)) = 21.3
Square Root( (337 * X^2) ) = 21.3
Square Root(337) * X = 21.3
18.3575 * X = 21.3
X = 21.3 / 18.3575
X = 1.16028

(Oops, should have checked again before I posted. Peter beat me.)

16 * 1.16028 = 18.5646 = Long Side
9 * 1.16028 = 10.4426 = Short Side
 
Last edited:
Well, at least I am impressed!

You guys are good. Just goes to show the depth of knowledge we are fortunate to have access to here on PLCs.net. :site:
 

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