Math help :-)

[The Medway Handyman]

An awning is attached to a wall at a height "X".

The front edge is lower because the awning slopes by 15 degrees.

Depending on the width, the awning could extend by anything from 1m to 4m.

If I want the front edge at a specific height "Y", what would distance "X" be?

I want to make up a spreadsheet to calculate this for any height "Y" and any extension. So, if the client wants the front of the awning 2.1m off the ground and it extends 2m, how high would "X" be?

[Huge]

Everything you need to know is in this article;

[Tim Streater]

Well if it slopes 15deg then the angle it makes with the wall is 90-15 =

75deg. So if it extends out Z (which you say is 1m to 4m), then that's the hypotenuse of the triangle in which case the vertical height of the triangle is given by:

H / Z = cos 75

So:

H = Z * cos 75

But you said the front edge is up by 2.1m so that gives you:

X = 2.1 + H

or X = 2.1 + (Z * cos 75)

if Z=2 then I type this into Google:

2.1 + (2 * cos (75 deg))

and it gives me 2.617....

No need for a spreadsheet at all.

Here's the diagram

. |\ | \ | \ | \ Z | \ |H \ | \ | \ | \ .---------. | | | | | 2.1 | | |

[tim.....]

or even a calculator

cos (75) is 0.258

so rounding it down a bit it's

Y +0.25(Z)

tim

[Frank Erskine]

SOHCAHTOA.

[Ramsman]

My understanding is that 2m is the horizontal distance ('it extends out Z'), so it's different from that.

|\ | \ | \ | \ | \ |X-Y \ | \ X| 15\ --------- | Z | | | Y | | |

(X-Y)/Z = tan 15 . . . X = Y + Z (tan 15)

Spreadsheet with Y in A1, Z in B1, then C1 is =A1+(B1*TAN(RADIANS(15))) which gives 2.64 for the given values.

HTH

[Farmer Giles]

Tan @ 15 degrees is your calculation = 0.268. That is then the ratio between the width of the awning and the increase in height.

[Mike Barnes]

The Medway Handyman :

The easy way to answer this and similar questions is to make a scale drawing. It doesn't have to be anything fancy, all you need is pencil, paper, and ruler.

A spreadsheet would be quicker and more accurate but a drawing would be accurate enough and would give you a better feel for what the result would look like.

[Chris Hogg]

X = Y + A, where A is the additional height of the attachment to the wall above the outer edge of the awning.

I'm not sure whether you're measuring the width of the awning horizontally out from the wall, or diagonally down the slope, i.e. the unrolled length, as it were.

If the width of the awning, call it W, is measured horizontally out from the wall, then A = W*Tan(15)

and X = Y + W*Tan(15) i.e. X = Y + 0.268*W

If the width of the awning, W, is measured down the slope, then A = W*Cos(15)

and X = Y + W*Cos(15) i.e. X = Y + 0.256*W

[Dave W]

I assume you mean 15 degrees below horizontal. "Depenfing on the width" - of what, measured how? I assume you measure the extension E down the sloping face, not horizontally.

X=Y+Esin15 i.e. X=Y+(0.26 x E) Your example would be X=2.1 + 0.26x2, i.e. 2.62m

If you can add the Y in your head, all you need to remember is that X is 0.26xE above Y.

[AnthonyL]

Oswald Has Been Here Obtaining Beer (but nothing to remember which was which - Sine, Cosine, Tan) B=base [from at least 50yrs ago :( ]

[Tim Streater]

Well, only Our Dave knows whether the Z refers to the length of material that has unrolled from the sunroof (my interpretation) or refers to the horizontal distance extended (your interpretation).

Either way, once you have the formula, no spreadsheet is needed. I just typed my formula straight into Google and it gave me the answer.

[Ramsman]

As we were always told at school, read the question. TMH said 'I want to make up a spreadsheet to calculate this for any height "Y" and any extension.' Hence my reply and my formula.

[Bill Wright]

Personally I'd do a scale drawing and use that. This sort of thing

Bill

[Tim Streater]

And I'm pointing out that you don't need one. For any given extension, just get google to do it or use your handy pocket calculator. A spreadsheet is overkill - unless you are learning spreadsheets. But then we weren't told that.

[Ramsman]

'I want to make up a spreadsheet to calculate this for any height "Y" and any extension.'

Perhaps you don't need one, but that's what he clearly asked for, so that's what I gave him. Having set it up, you only have to enter the values and recalculate each time.

[Farmer Giles]

You can make up an Excel spreadsheet as follows:

Put in awning front height - in metres - in column (say) D3

Then put the awning width (by that I mean front to back) - again in metres - in column D5

Then put the slope - in degrees - in column D7

Your final column, which will give the height of the rear of the awning, will need the following formula: =TAN(D7*PI()/180)*D5+(D3)

[John Rumm]

If the extension is the horizontal reach, then it might be simpler to simply think of the slope as a rise in terms of "1 in 4" or similar...

So a 2m extension translates as 0.5m rise at that going.

[tony sayer]

Yes fine but often it seems that Wikipedia goes into some complex maths rather too soon in the explain process. I 'm sure 'tho I can't remember it there is a very good site around that has a few worked out examples and shows you how those are done thats rather more educative than this one...

[GMM]

This is the easy way (although the calculation isn't all that complicated)