Calculate interior angles of irregular pentagon

[Flynnwood]

Hi,

I am using 12cm wide decking board to finish off the top of a pond. I have an external perimeter total of 4.995 metres.

How can I calculate the interior angles f,g,h,i,j, please? (The picture is rough drawn so not to scale)

 

[Steve Maskery]

I don't think that there is enough info there to give a definitive answer, there are an infinite number of solutions.
I fyou can also provide some corner distances, then it is easy to do.

 

[flh801978]

As Steve says there's a dimension missing to make it work in only one way
If you could give dimension J to H it will work and the others can be calculated

Ian

 

[RobinBHM]

Convert each angle into a right angle triangle.

For eg, take a vertical line down from point 'g'
then a horizontal line across from point 'h'

The intersection if these 2 lines will be 90 degrees and you can easily work out the angle. Search online for right angled triangle solver.

Once youve done the first one, it fixes all the rest, which you can then work round with right angled triangles for each.

There is an app called that which you csn use on your phone or tablet.

 

[nev]

Would this work?
http://www.finehomebuilding.com/2012/11 ... ring-tools

 

[Steve Maskery]

Robin, I think that that works only for the specific case of that particular sketch. But it is rough and not to scale, so we need some more info in order to get the solution he needs.
Imagine 5 strips of wood, pinned loosely at the ends to make that shape. It could be wiggled around all over the place without altering the lengths, but the angles would continuously change.

 

[Steve Maskery]

We need two of the three corner-to-corner distances.

 

[thick_mike]

Can you not just cut the boards at right angles to the exterior dimension, then lay them out and scribe interior and exterior crossover points? You might lose a couple of feet of waste, but the mitres should be spot on without any need for SOH-CAH-TOA!

 

[RobinBHM]

Robin, I think that that works only for the specific case of that particular sketch. But it is rough and not to scale, so we need some more info in order to get the solution he needs.
Imagine 5 strips of wood, pinned loosely at the ends to make that shape. It could be wiggled around all over the place without altering the lengths, but the angles would continuously change.

Ah yes, very true. My apologies for some wrong info. Im not that with it on a bank holiday Monday

 

[Bigdanny]

STeve has hit the nail on the head. You need at least one known angle or another hypotenuse between 2 of the sides.

 

[Flynnwood]

Thanks for replies so far

Here is additional info.

Nev - that was a good link, now bookmarked.

 

[Steve Maskery]

The slight discrepancy is because SketchUp draws circles as polygons, but this is not far off.

Mine's a pint
(Unfortunately, at the mo, it is a pint of Lemsip )

 

[Flynnwood]

Cheers Steve - much appreciated =D>

ccasion5: << a Virtual Lemsip