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How to calculate
How do I calculate this length. These boards meet at center top 45ed together and then extend down to wall where it meets them at a 45. Width needs be 84. How do I find out using math how long to make the pieces
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You need to draw that triangle a little more accurately. What I think you are depicting is an isosceles triangle. That is a triangle having 2 equal legs. That would be the legs going from the top to the wall.
In a triangle all angles must add to 180 degrees. In this case you have a right triangle at the top so this is a right isosceles triangle. The ratio of the legs in a right isosceles triangle is 1:1:square root of 2. You have specified that 84 is the length of the side that has the ratio of the square root of 2.
therefore your other 2 sides are 84 divided by 1.414 = 59.41 inches.
George
In a triangle all angles must add to 180 degrees. In this case you have a right triangle at the top so this is a right isosceles triangle. The ratio of the legs in a right isosceles triangle is 1:1:square root of 2. You have specified that 84 is the length of the side that has the ratio of the square root of 2.
therefore your other 2 sides are 84 divided by 1.414 = 59.41 inches.
George
The Following 2 Users Say Thank You to GeorgeC For This Useful Post:  Onefreetexan (06192019), wretched64 (06192019) 
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Quote:
Originally Posted by GeorgeC
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You need to draw that triangle a little more accurately. What I think you are depicting is an isosceles triangle. That is a triangle having 2 equal legs. That would be the legs going from the top to the wall.
In a triangle all angles must add to 180 degrees. In this case you have a right triangle at the top so this is a right isosceles triangle. The ratio of the legs in a right isosceles triangle is 1:1:square root of 2. You have specified that 84 is the length of the side that has the ratio of the square root of 2.
therefore your other 2 sides are 84 divided by 1.414 = 59.41 inches.
George
In a triangle all angles must add to 180 degrees. In this case you have a right triangle at the top so this is a right isosceles triangle. The ratio of the legs in a right isosceles triangle is 1:1:square root of 2. You have specified that 84 is the length of the side that has the ratio of the square root of 2.
therefore your other 2 sides are 84 divided by 1.414 = 59.41 inches.
George
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The top angle, is it a 45 degree angle or two miters making it a 90 degree angle?
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I read it as 2 45's.
Hard to tell several areas, that is why I suggested more accurate drawing.
George
Hard to tell several areas, that is why I suggested more accurate drawing.
George
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Quote:
Originally Posted by wretched64
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Yeah I just hand drew it. We dont make things perfect here until they are built. Lol. Thanks
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If you want good answers, you must at least make them good enough so that responders can tell what it is that you intend to build.
George
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Quote:
Originally Posted by GeorgeC
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If you want good answers, you must at least make them good enough so that responders can tell what it is that you intend to build.
George
George
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Quote:
Originally Posted by Steve Neul
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The top angle, is it a 45 degree angle or two miters making it a 90 degree angle?
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https://www.spikevm.com/calculators/...terlength.php
Is this a shed roof? No matter as the calculations would be the same. Your drawing shows a 45 degree angle , which is a 12/12 pitch. Enter half of 7' (84") into the equation as the width and there you go.
Google how to calculate common rafter lengths and it will be clear. You might also read up on using a framing square as you can use it to step off lengths and then add any overhangs if you want and its just good to know how to use one.. They were the original calculators.
Or, you could just draw it out on a piece of plywood if you have one.
Is this a shed roof? No matter as the calculations would be the same. Your drawing shows a 45 degree angle , which is a 12/12 pitch. Enter half of 7' (84") into the equation as the width and there you go.
Google how to calculate common rafter lengths and it will be clear. You might also read up on using a framing square as you can use it to step off lengths and then add any overhangs if you want and its just good to know how to use one.. They were the original calculators.
Or, you could just draw it out on a piece of plywood if you have one.
Member
Quote:
Originally Posted by Frost
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https://www.spikevm.com/calculators/...terlength.php
Is this a shed roof? No matter as the calculations would be the same. Your drawing shows a 45 degree angle , which is a 12/12 pitch. Enter half of 7' (84") into the equation as the width and there you go.
Google how to calculate common rafter lengths and it will be clear. You might also read up on using a framing square as you can use it to step off lengths and then add any overhangs if you want and its just good to know how to use one.. They were the original calculators.
Or, you could just draw it out on a piece of plywood if you have one.
Is this a shed roof? No matter as the calculations would be the same. Your drawing shows a 45 degree angle , which is a 12/12 pitch. Enter half of 7' (84") into the equation as the width and there you go.
Google how to calculate common rafter lengths and it will be clear. You might also read up on using a framing square as you can use it to step off lengths and then add any overhangs if you want and its just good to know how to use one.. They were the original calculators.
Or, you could just draw it out on a piece of plywood if you have one.
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And 59.41 was exactly the length need for Long to short with 84 being the hard measurement. Tha is for help
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The 59.41 sounds right. I drew it to scale and came up with 59".
Senior Member
I used the Pythagorean Theorem and got the same answer: 59.4 inches. Because of the way the angles are cut, the inside length and outside length are the same.
Side length = sqrt((84^2)/2) = 59.4
Side length = sqrt((84^2)/2) = 59.4
Quote:
Originally Posted by wretched64
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Yeah I just hand drew it. We dont make things perfect here until they are built. Lol. Thanks
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Tony B
Retired woodworker, amongst other things, Sold full time cruising boat and now full time cruising in RV. Currently in Denison, Tx
Senior Member
Quote:
Originally Posted by GeorgeC
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You need to draw that triangle a little more accurately. What I think you are depicting is an isosceles triangle. That is a triangle having 2 equal legs. That would be the legs going from the top to the wall.
In a triangle all angles must add to 180 degrees. In this case you have a right triangle at the top so this is a right isosceles triangle. The ratio of the legs in a right isosceles triangle is 1:1:square root of 2. You have specified that 84 is the length of the side that has the ratio of the square root of 2.
therefore your other 2 sides are 84 divided by 1.414 = 59.41 inches.
George
In a triangle all angles must add to 180 degrees. In this case you have a right triangle at the top so this is a right isosceles triangle. The ratio of the legs in a right isosceles triangle is 1:1:square root of 2. You have specified that 84 is the length of the side that has the ratio of the square root of 2.
therefore your other 2 sides are 84 divided by 1.414 = 59.41 inches.
George
Member
Wall up and letters attached
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