See if you can bring construction and calculation together in forrowing example and compare the results:

on my iPhone I make it:

8426.149773176359

Its the square root of 71 million.

Interestingly Excel says thats exactly 8426.149773176300000000

But my phone says 8426.149773176359 which is strange

Sorry @DaveR, unfortunately your construction is off. Did you use the ‘Pie’ tool? That should give you a different value if applied correctly.

Calculation somewhere along the line shows that the length is sqrt(71). Boosts my trust in SketchUp.

Apply the ‘Pie’ tool on A-B

No. I didn’t use the Pie tool.

That probably explains the difference.

I didn’t see any reason to use the Pie tool. It was a simple enough construction without it. But nevermind.

Interesting.

How did you set that out in SketchUp to get such an accurate length?

The best I can do is 8426.105385 using a circle with the correct radius and the maximum 999 segments which obviously isn’t spot on?

The ‘Pie’ tool (and the ‘Arc’ tool) provides a **true** arc intersection. The ‘Circle’ tool still uses a segmented circle.

Sorry - but I still cant get that to work.

What length did you set the Pie Tool radius to?

It should be sqrt of 80M = 8944.271909999159

I didn’t set the radius in ‘Entity Info’ to… other than using the dotted edge A-B (see image above) as the radius for the ‘Pie’ tool. Rotate this edge about A to get the pie’s intersection with the horizontal edge (which was larger to begin with).

I get 8,426.1497731763586306341399062027.

Continue the calculation to the end → sqrt(71)

If somewhere in the middle of the proces you input value like 8944.271909999159, SketchUp’s ‘Entity Info’ might round the input. *Either calculate all te way through or be lazy and let SketchUp help you.*

Yes - I tried that method as well but I cannot get the exact figure you are showing. I am always a few tenths or sometimes a few hundredths off. Also my pie radius is definitely segmented - I wonder if there is there a setting somewhere that makes it a true radius?

…2027 should be …2327

I can’t get the Pie tool to find the exact intersection of two arcs - it will snap to the segments instead. The figure could be at any angle, it is not given that the line with the length to be determined is horizontal.

See the 90 degrees angles in the first image.

I think you only need one arc.

The line with the length to be determined is at right angles to the 3000mm vertical line.

The hypotonuse is sqrt 80M = 8944.271909999159 +/- but I cannot get that radius to intersect the horizontal line and give the AB line length accurately?

You’ll need to wait till you see the intersection cross (red near “From Point”)

@Anssi, only one arc can be handled as true arc at a given time. But then only one (‘Pie’) is needed to intersect the horizontal edge.

I hope you didn’t miss the right angle in the upper left corner.

Even with 64-bit numbers, you generally can only get 16-17 significant figures in base 10. Excel limits these to 15 sig-figs.