Questions on the construction of geometrical figures using a limited set of "tools".

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7
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4answers
174 views

Construction of a triangle

I need to construct a triangle with given information: $c = 6$, $h = 4$ and $\alpha - \beta = 30º$. I'll put approximate result for any clarification.
2
votes
2answers
231 views

Construction of a triangle, given: side, sum of the other sides and angle between them.

Given: $\overline{AB}$, $\overline{AC}+\overline{BC}$ and $\angle C$. Construct the triangle $\triangle ABC$ using rule and compass.
7
votes
0answers
119 views

Which power means are constructible?

The three classic Pythagorean means $A$, $G$, $H$ (arithmetic, geometric, and harmonic mean respectively) of positive real $a$ and $b$ have a cute geometric construction, as does the quadratic mean ...
1
vote
1answer
757 views

Find the maximum area possible of equilateral triangle that inside the given square

How can I find the maximum area possible of equilateral triangle that inside a square whose sides have length a. And how does that triangle look like? Can we construct it (with compass and ...
2
votes
2answers
237 views

Doubling the cube neusis

Can anyone explain me in simple maths the neusis construction at http://en.wikipedia.org/wiki/Doubling_the_cube#Using_a_marked_ruler? Why and how does it produce the $\root 3 \of 2$?
3
votes
1answer
31 views

Computational compass-and-straightedge constructions

I recently came across Ancient Greek Geometry, a web toy by Nico Disseldorp, and it got me wondering: is there a way to exactly model the points generated by geometric constructions, starting from two ...
4
votes
1answer
55 views

Is the non-existence of a general quintic formula related to the impossibility of constructing the geometric median for five points?

In particular, in the Computation section of in the Wikipedia page for geometric median, there is this statement: ...but no such formula is known for the geometric median, and it has been shown ...
3
votes
2answers
67 views

Drawing a triangle from medians

Is it possible to draw a triangle, if the length of its medians $(m_1, m_2, m_3)$ are given only? Someone asked me this question, but I can not see it. Is it really possible? UPDATE Apart from the ...
2
votes
2answers
43 views

Construction of a point with resprect to a triangle

For a given triangle $ABC$, how to construct a point $P$ such that $PA \colon PB \colon PC = 1 \colon 2 \colon4$?
2
votes
1answer
38 views

How to embed this circle tangent to the other circles?

I want to construct a circle that would be tangent to the $3$ circles and would have its diameter lie somewhere on the segment $BI$. $EF$ includes the diameters of the $3$ given circles. $EB=BF$. ...
40
votes
17answers
2k views

How to create circles and or sections of a circle when the centre is inaccessible

I am doing landscaping and some times I need to create circles or parts of circles that would put the centre of the circle in the neighbours' garden, or there are other obstructions that stop me from ...
1
vote
1answer
41 views

A construction of a triangle mapping with a homothety

Given an acute triangle $ABC$ draw a triangle $PQR$ such that $AB=2PQ,BC=2QR,CA=2RP$, and the lines $PQ,QR,RP$ pass through $A,B,C$ respectively. Note $A,B,C,P,Q,R$ are distinct. This is a problem ...
3
votes
2answers
253 views

Geometric construction of logarithms

Can you draw a logarithmic scale just using some clever geometric construction? Or can it only be done using an actual table of logarithms? (It's obviously trivial to draw a linear scale. It isn't ...
2
votes
2answers
48 views

How to construct the point of intersection of a line and a parabola whose focus and directrix are known?

I found this problem in Polya's "How to solve it". It goes as follows Using only a straight edge and a compass, construct the point(s) of intersection of a given line and a parabola whose focus ...
1
vote
1answer
52 views

Prove : for every integer $n\ge1$, if the regular $n^2$-gon is constructible, then $n$ has no odd prime divisors.

For every integer $n\ge1$, if the regular $n^2$-gon is constructible, then $n$ has no odd prime divisors. I know is has something to do with the fact the output Euler's Totient function on $n^2$ ...
0
votes
0answers
26 views

Geometric question (middle line of a parallelogram)

Let $ABCD$ be a parallelogram and $I,J$ are two points such that $AI = ID$ and $BJ = JD$. Show that ($IJ$) is parallel to ($AB$).
5
votes
0answers
38 views

Geometrical construction of 7th roots of unity given parabola x^2

Given parabola $x^2$ on plane, how can I construct 7th roots of unity? I was straying with my only idea, that sum of squares of real and imaginary part of roots of 1 equals 1 and belongs to ...
1
vote
0answers
18 views

Given a pair of conics, construct (synthetically) their shared tangent lines

There are various well-known ways to construct the common tangents to a pair of circles; this is an easy one. I also just learned that we can use Pascal's Theorem to construct a tangent to a conic at ...
0
votes
1answer
29 views

Geometric proof of dot product distributive property

I'm working my way through a text book for fun in order to keep my math brain fresh and came across this simple yet perplexing problem. "Demonstrate geometrically that the dot product is ...
1
vote
1answer
34 views

How to prove by induction the constructibility of a line segment of length $\sqrt{n}$?

How to prove the following statement by induction? If a line of unit length is given, then a line of length $\sqrt{n}$ can be constructed with straightedge and compass for each positive integer $n$. ...
0
votes
0answers
41 views

Straightedge-Compass Construction vs Origami

I've been looking into these two types of geometric construction and I was wondering- why is origami capable of solving up to cubic equations, when straightedge-compass construction is only capable of ...
0
votes
0answers
31 views

Dummit & Foote: Construction of the regular $17$-gon

In the last step of the exercise where we construct the $17$-gon, I have to draw a circle with a diameter whose endpoints are $(0, 1)$ and $(\eta_1', \eta_4')$ and show that it intersects the positive ...
9
votes
3answers
11k views

Compass-and-straightedge construction of the square root of a given line?

Given A straight line of arbitrary length The ability to construct a straight line in any direction from any starting point with the "unit length", or the length whose square root of its magnitude ...
1
vote
1answer
40 views

Is the given triangle unique?

I was reading Polya's How to Solve It when I came across the following problem. Construct a triangle with an angle, the length of altitude through that angle and the perimeter of the triangle given. I ...
5
votes
1answer
562 views

History of Compass/Straight Edge Construction

I'm interested in learning the origin of compass/straight-edge constructions. In particular, I am interested in the historical interplay between Euclid's axioms for plane geometry, and ...
0
votes
1answer
26 views

Ramanujan (LPS) graph construction

In the original LPS article they mention two constructions for Ramanujan graphs, one with order $q^3$ nodes and the other in order $q$. My question is regarding the second construction (which is ...
0
votes
1answer
63 views

Logic behind a Geometric Construction of regular heptadecagon

I'm reading a Chinese book "Methods of Mathematical Physics" by Wu Chongshi. During introduction of complex analysis, it explains a Geometric Construction of regular heptadecagon. Task: to achieve ...
0
votes
0answers
15 views

calculate the radius of a sphere-like cloudpoint(not in the origin)

how would you calculate the radius of a piece of a sphere-like(sphere with noise) cloud point matrix(The cloud point represents the surface) which center is not necesarily in the origin. if it was ...
0
votes
0answers
43 views

proof of construction of angle 360/17

One construction for a 17-sided polygon is shown below. ...
1
vote
0answers
26 views

To construct a right triangle given the hypotenuse and sum of two legs [duplicate]

NOTE: I want a hint only. A compass and a straightedge construction:Given a hypotenuse and the sum of lengths of the legs,we need to construct a right triangle. MY TRY: From any ray $BE$, ,let ...
0
votes
1answer
17 views

construction of a line.

Two non parallel lines l & m are given. For given two angles A & B we have to construct a line n such that it makes angles A & B with lines l & m respectively. Line n intersects l ...
0
votes
2answers
29 views

Construction of pentagon with all sides and alternative two angles given.

All sides of a pentagon ABCDE are given. Angles A & C are given. Can such pentagon be created by straightedge and compass?
0
votes
2answers
28 views

Some help needed with a geometry question

What is a formula for all integers n for which a regular polygon with n sides can be constructed using a ruler and compass construction?
0
votes
0answers
27 views

Minimum components required to construct a unique polygon

What is the minimum components required to construct a unique n sides polygon? If k is a such number for n sided polygon for any k given components polygon can be constructed by compass and ...
0
votes
1answer
13 views

Geometric Sequence with Normal Distribution Problem

Given: The running time (in seconds) of an algorithm on a data set is approximately normally distributed with mean 3 and variance 0.25. a. What is the probability that the running time of a run ...
1
vote
1answer
23 views

Constructing “strange” sets by removing elements: Is there any comparison?

Recently I had a thought about some sets with special properties that are constructed from a starting set $A$ and successively removing elements from it. I am not an expert in set theory but perhaps ...
0
votes
0answers
30 views

geometric construction puzzle is my construction right?

I think I solved my own question of hyperbolic geometry (and circle ) construction problem but am not sure if it is correct, it looks that way but can somebody help me with prooving it? My ...
2
votes
2answers
93 views

triangle construction given side, angle and median

I can't figure out the solution to this, it looks to me like it doesn't have any solution but I need some proof. problem: Construct a triangle ABC with given $a=6 cm$ $\alpha=75^\circ $ and ...
1
vote
1answer
118 views

hyperbolic geometry (and circle ) construction problem

Was thinking about hyperbolic geometry, the Poincare Disk Model and Sweikarts constant and combined them all in a construction puzzle that I was unable to solve. My construction puzzle: Given: A ...
0
votes
2answers
42 views

Construction by compass and straightedge.

l,m,n are three concurrent line concurrent at point A. Given a point B on line l. Is it possible to construct point C on line n such that line m is a median of triangle ABC
0
votes
1answer
87 views

What are some alternative ways of describing n-dimensional surfaces using control points other than Bezier surfaces?

I'm interested in problems involving geometric constraints and curve subdivision. I noticed that most of these problems describe the curves/surfaces using the Bezier form. I wanted to know if there ...
10
votes
1answer
93 views

Using a compass and straightedge, what is the shortest way to divide a line segment into $n$ equal parts?

Sometimes I help my next door neighbor's daughter with her homework. Today she had to trisect a line segment using a compass and straightedge. Admittedly, I had to look this up on the internet, and ...
1
vote
1answer
84 views

To draw a straight line tangent to two given ellipses

How can I draw a a straight line that touches two ellipses? There are, like for two circles, 4 different solutions. I´m not interested in the analytical solution, but in the geometrical drawing, ...
0
votes
0answers
17 views

Open Construction Problems [duplicate]

Are there still any problems in ruler-and-compass construction that remain unsolved? Or have all of the open questions already been answered?
2
votes
3answers
2k views

Construction of 145 degree angle

I've tried doing it but I end up only constructing 135 degree angle.I have to use ruler without divisions and compass.It must be done with system of isosceles and equilateral triangle and their ...
2
votes
0answers
61 views

Computing an area with geometric methods

Consider the construction below (it is self-evident, no tricks or misleading drawing) What is the area enclosed by the curve that goes through the points H,J,M,L ? I solved the problem using ...
1
vote
1answer
47 views

Geometric construction of 2 soap bubbles meeting

When 2 soap bubbles meet, you get a dividing wall between the soap bubbles. Plateau concluded that the three spheres (2 soap bubbles and the dividing wall) meet at angles of 120. Here's an ...
0
votes
1answer
64 views

What are four ways to quadrisect any triangle?

What are four ways to quadrisect any triangle with compass and straightedge? I have a few already: Draw a median and from the midpoint, draw two medians to the remaining sides. Draw a median and ...
2
votes
1answer
124 views

The Basel Problem and Theodorus' Spiral

I've been trying to find a classical solution to the famous Basel Problem solved by Euler. To those unfamiliar the problem is to find the sum infinite series made up of the reciprocals of square ...
-1
votes
2answers
2k views

Making an angle of 10 degree and its multiple using compass?

We all know very well how to make an angle of 15 and 45 degree and its multiple using compass. Can anybody tell me how to make an angle of 10 degree and its multiple using compass?