Draw a 145 degree angle without a protractor

[145]

How to draw a 145 degree angle without a protractor?
It is easy to draw 150 degree but how to draw a 145 degree angle?

[leesajohnson]

How to show here I don't understand.

[Guest]

It is impossible to draw a 145 degree angle using only a compass and straight edge.

If it was possible you could construct an angle of 5 degrees by using the construction for 150 degrees, then by combining 4 lots of 5 degree angles you could get an angle of 20 degrees, which has been famously shown to be not constructible in the proof that (general) trisection of angles is impossible.

It is possible to get 145 degrees but you have to employ some additional tool, see
https://en.wikipedia.org/wiki/Angle_tri ... er_methods
using these methods you can trisect 60 degrees, to get 20 degrees, then bisect twice to get 5 degrees, and add multiple lots of 5 degrees together to get 145 degrees.

Hope this helped,

R. Baber.

[Guest]

I think all you need to do is take an A$ page of paper, fold it in half....gives you A5 size.

Fold the A5 diagonally ...this gives you 35 degrees...... 180 - 35 = 145.

Done

[Guest]

take an A$ page of paper

........should be A4 page of paper

[Guest]

Folding by the method described gets you an angle of 35.264... degrees not 35 degrees.

You can get 145 degrees by folding but it is a lot more complicated then just folding an A4 sheet twice.

R. Baber.

[Guest]

Yes, OK, accepted, but.....The question was to draw an angle, and that need accuracy. Every time you fold paper and add it to something already folded accuracy soon disappears.

[Guest]

Thanks for post

[Guest]