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Building a Darkroom: 3-4-5 rule for right angles
The 3-4-5 rule for making square corners
Pythagoreous' Theorem: the hypotenuse is the square root of the sum of the squares of the sides for a right triangle 3x3 + 4x4 = 5x5So, if one side of a triangle is 3 units, the other side 4 units, and the diagonal is 5 units, the corner between the 3 and 4 unit sides is square. How do you use this rule? Measure one side, divide this by 4, to give you the size of 1 unit (round off to make it easy), mark this point. Measure the other side for 3 units from the corner, mark this point. Measure from point to point, it should be 5 units. For example, using a room slightly smaller than 8' (96") I chose a unit of 18". 4 times 18" is 72", so I measured from the corner to a point 72" away, and marked that point. Next I measured 54" along the other side (3 times 18") and marked that point. By adjusting the angle until the distance between these two marked points was 90" (5 times 18") I new that the corner was square. Also, when the room has sides of the same length (a rectangle), the distance from one corner to another should match the opposite corner distances (the length of the blue line is the same as the length of the green line)
Visitor Comments
The comments stated below are not necessarily the opinions of Andy Hughes or DarkroomSourceyour picture says the 5 side is 80 your verbage says 90 verbage is right picture is wrongAnonymously contributed on 2006-06-08 13:01:01
Wow!Contributed by on 2006-06-09 06:49:35
This page has been on the internet for about 10 years, and thousands of people have visited this site, and no-one has ever caught that before!
I am impressed - and embarrassed
