What is the 3,4,5 rule in finding a 45 degree angel?

Question

Forgot the system in using it. Thanks. Did I explain it right even?

Answer 1

I'm guessing what your looking for is the old carpentry trick for squaring up perpendicular lines. To use the 3, 4, 5, rule you measure and mark 3 feet from the intersection on one line, and 4 feet on the other line. The measurement diagonally from mark to mark will be exactly 5 feet only if the angle is exactly 90 degrees. BTW This trick can be made more versatile by applying a little more algebra to the Pythagorean theorem. nA^2 + nB^2 = nC^2 is an equivalent equation and the implication is that you can multiply all sides of a 3, 4, 5, triangle by an equal factor. The advantage for this is as follows. Say you are checking the walls of a building 20' x 25' to see if they are square. You then find a factor you can multiply 3 and 4 by that's as large as possible without exceeding the wall length. I this case a factor of 6 works best. So then you measure 18' (3'x6) down the 20' wall and 24' (4'x6) down the 25' wall and then measuring diagonally you will get a measurement of exactly 30' (5'x6) if the walls are at a perfect 90 degree angle. You can also use this trick for objects smaller than 3' x 4' by using 3, 4, and 5 inches instead of feet. For example you want to square a picture frame 22" x 32". The greatest factor in this case is 7. Thus you make a mark at 21" (3" x 7) and at 28" (4" x 7) and the measurement from mark to mark diagonally will be 35" when square. On Square or rectangluar objects it's actually easier to check the corners for squareness by making sure that the length from one corner to the diagonally opposite corner equals the length between the remaining two corners. One last trick is if your using the same dimensions for repeated checks you may find it convienient and more accurate to cut a stick the length of the hypotenuse instead of trying to hold and read a kinked measuring tape.

Answer 2

The 3,4,5 rule is the Pythagorean theorem

where 3^2 + 4^2 = 5^2

and gives the dimension of the 3 sides of a right triangle

Answer 3

3 4 5 Rule

Answer 4

4 5 Rule

Answer 5

When your working with 45 degree angles, the numbers used for finding distances of the lines is 1, 1, and sqrt of 2. The 3, 4, 5 rule is based on angles of 36.87 and 53.13.

3/4 = tan(36.87)
4/3 = tan(53.13)

What you can do by knowing that it is a 3, 4, 5 triangle is you can determine the length of segments that correspond to the numbers.

Say you know the length of the segment that corresponds to 5. If you want to know the length that corresponds to 3 then set up a ratio.

3 / 5 = x / (length given)

This will give you the value for x.

Answer 6

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Since the triangle is isosceles, we have BA = CA = 7 cm. Furthermore, m∠BAC = 180° - m∠ABC - m∠CBA = (180-45-45)° = 90°, so BA and CA are perpendicular. Therefore the area of the triangle is (1/2) BA * CA = 24.5 cm^2.

Answer 7

3,4,5, will give you a right triangle.
It's not a 45 Deg. triangle.
Bisect the right angle to get 45 Deg.

Answer 8

4 , 4 , 5.66 . Angle between the long side and either short side is 45deg. You can use 12/12/17 if you re want nice round numbers or whole inches).

(4^2 + 4^2 = 5.66^2 apprx)

Answer 9

one side is 3 one side is r making the 3rd side 5