- posted on December 31, 2006, 10:23 pm

I know the method is rattling around back there amongst the unused and as yet unkilled brain cells but I can't seem to come up with it.

Thanks to the more mathmatically inclined.

jc

- posted on December 31, 2006, 10:38 pm

It's not the same for each degree of angle (the gain going from 0 to 1 degree is a lot larger than the gain when you go from 88 to 89).

Since the tangent of an angle (a) is equal to the rise (y) divided by the run (x$), you can calculate:

tan(a) = y / 24

y = 24 * tan(a)

If a1 is your starting angle then

y1 = 24

and the gain for that 1 degree difference is

y2 - y1 = 24 * (tan(a+1) - tan(a))

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto

- posted on December 31, 2006, 10:40 pm

Morris Dovey wrote:

| It's not the same for each degree of angle (the gain going from 0 | to 1 degree is a lot larger than the gain when you go from 88 to | 89).

I think I said that backward. :-(

larger --> smaller

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto

| It's not the same for each degree of angle (the gain going from 0 | to 1 degree is a lot larger than the gain when you go from 88 to | 89).

I think I said that backward. :-(

larger --> smaller

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto

- posted on December 31, 2006, 10:50 pm

I am not going to attempt ASCII art.

If by the "square corner" you mean the two sides of a right angle triangle which are orthogonal (90 degree angle between these sides, then the formula is

Height = Length * Tangent(opposite angle).

For Length = 24 inch and opposite angle = 1 deg, then Height = 0.418922

If you have MS Excel, then you can enter a formula Cell for Height = Îll for Length*TAN(RADIANS(Cell for angle))

For some strange reason MS designed Excel to use RADIANS in angle functions instead of degrees where 180 deg = PI Radians.

Dave Paine

If by the "square corner" you mean the two sides of a right angle triangle which are orthogonal (90 degree angle between these sides, then the formula is

Height = Length * Tangent(opposite angle).

For Length = 24 inch and opposite angle = 1 deg, then Height = 0.418922

If you have MS Excel, then you can enter a formula Cell for Height = Îll for Length*TAN(RADIANS(Cell for angle))

For some strange reason MS designed Excel to use RADIANS in angle functions instead of degrees where 180 deg = PI Radians.

Dave Paine

- posted on December 31, 2006, 10:52 pm

As Morris Dovey warned in a separate message, the height is not linear for
each degree. Hence you do need to use the formula.

Dave Paine

Dave Paine

- posted on December 31, 2006, 11:28 pm

Assuming the 24" side is included between the right angle and the angle to be incremented, and the 24" side and the 'gain' side are at right angles to each other:

Gain in inches = 24*tangent(incremented angle).

For some angles: 1 deg-> .4189516" 2 deg-> .8380985 15 deg -> 6.4307806" 22.5 deg-> 9.5941125" 30 deg -> 13.8564061" 45 deg -> 24.0000000" 89 deg-> 1,374.9590791" etc.....

Using Windows calculator makes the computation easy once you know the equation.

Tin Woodsmn

Happy New Year to all of the Wreckers....

- posted on January 1, 2007, 3:56 am

What do you mean by "gain" ? If you mean, for a right triangle with angel A between the hypotenuse and a 24" side, that the "gain" is the length of the side opposite angle X, then the change in the length of that side is not a linear function wrt the angle X. However, it will be equal to 24 X sine(A)

--

Often wrong, never in doubt.

Larry Wasserman - Baltimore, Maryland - snipped-for-privacy@charm.net

Often wrong, never in doubt.

Larry Wasserman - Baltimore, Maryland - snipped-for-privacy@charm.net

Click to see the full signature.

- posted on January 1, 2007, 5:12 am

OOPS, maybe a little doubt would be good on this one.
G/HYP does = SIN X, but you have two unknowns, since the base is fixed at
24.
G = HYP*SIN X doesn't help, since we don't know the hypotenuse.
As Tin said, TAN X = G/24, so G = 24 TAN X.
I hope I'm not too sleepy to get this right.
WL

- posted on January 1, 2007, 6:28 am

You are right, I was mixing up my sides, the tangent is correct.

--

A man who throws dirt loses ground.

Larry Wasserman - Baltimore Maryland - snipped-for-privacy@charm.net

A man who throws dirt loses ground.

Larry Wasserman - Baltimore Maryland - snipped-for-privacy@charm.net

Click to see the full signature.

- posted on January 1, 2007, 1:03 pm

Funny story on that subject:

On of my aspiring architectural drafters was trying to make a model of his project with a 6/12 roof slope. The roof just wouldn't work out.

After lots of investigation, I found out that he had reasoned that if a 12/12 slope gives a 45 degree angle, a 6/12 should give a 22.5 degree angle. He just couldn't see my arguments to the contrary.

The only way I convinced him was to ask him to draw a roof slope at 24/12, and see if it produced a 90 degree angle....

Old Guy

On of my aspiring architectural drafters was trying to make a model of his project with a 6/12 roof slope. The roof just wouldn't work out.

After lots of investigation, I found out that he had reasoned that if a 12/12 slope gives a 45 degree angle, a 6/12 should give a 22.5 degree angle. He just couldn't see my arguments to the contrary.

The only way I convinced him was to ask him to draw a roof slope at 24/12, and see if it produced a 90 degree angle....

Old Guy

- posted on January 1, 2007, 3:10 pm

Thanks everyone for the help. In the original post, I neglected to mention
that I was calculating this for the first couple of degrees. I've got it
now.

Have a very happy and healthy New Year.

jc

Have a very happy and healthy New Year.

jc

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