# Investment: Table mental gymnastics for determination of elements with angular conditions

We have already used one “Table Mental Gymnastics” to study investment: a set of exercises that serve to stimulate thinking, develop and maintain an agile mind, automate processes calculation and analysis etc..

We now propose to raise a similar set of problems but aimed at obtaining solutions to basic problems of geometry. In this case we will raise finding circumferences passing through a given point and angular meet conditions on two circumferences.

# Learning Path Metric Geometry

In addressing the study of a science we can follow different paths that lead to learning. Chaining concepts linked to each other allow us to generate a mental representation of abstract patterns, facilitating their assimilation and subsequent application in problem solving.
In these pages two images that summarize a possible strategy or sequence of progressive incorporation of the basics of this branch of science in the education of our students are proposed.

# Problem of Apollonius : ccc

Any of the problems of tangents that are included under the name "Apolonio problems" can be reduced to one of the variants studied the most basic of them all: the fundamental problem of tangents (PFT).

In this case we will study what we call "Apolonio Case ccc", namely, If the problem of tangents in which the data are given by conditions tangents three circumferences (ccc).

# Investment: Table mental gymnastics processing elements

What is a table of mental gymnastics? We can say that is a set of exercises that serve to stimulate reasoning, develop and maintain an agile mind, automate processes calculation and analysis etc..
In the subjects of geometry we can propose a problem and make slight variations to any of the data. Variability problem will create families of exercises that emphasize one or more concepts of interest.

# Reversing a point. 10 constructions for obtaining [I- Metrics]

One recommendation I always do my students is to try to solve the same problem in different ways, instead of many times the same problems with almost similar statements.

We see a problem with metric or projective approaches in each case.

In one of my last classes we propose are obtaining the inverse of a point, an investment in the center and power is known. The proposed statement was as follows:

Since the square in Figure, in which one vertex is the center of inversion and the opposite vertex is a double point, determining the inverse of the point A (adjacent vertex).

# conic metric: Head circumference

We have defined the ellipse as the “locus of centers circumferences, through a focus, They are tangent to the focal circumference of the other focus center”.

This definition allows us to approach the study of the conic by applying the concepts studied to solve the problems of tangents and, en particular, reducing them to the fundamental problem of tangents.

This circumference will link with another whose radius is half the radius of the focal, and its center is the taper. We call this circumference “Head circumference”.

# Conic as Locus Centers Circumferences Tangents

We have seen that the study of conic can be made from different geometric approaches. En particular, to start analyzing conic we have defined as the ellipse locus, we said that:

Ellipse is the locus of points in a plane whose sum of distances from two fixed points, called Spotlights, It has a constant value.

This metric definition of this curve allows us to address important study relating to the tangents circumferences, known as “Problem of Apollonius” in any of its versions. When we approach the study of the parabola or hyperbola return to reframe the problem to generalize these concepts and reduce problems “fundamental problem of tangents in the case straight”, or “fundamental problem of tangents in the case circumference”, namely, determining a circumference of a “Make corradical” a tangency condition.

# Metric geometry : Investment beam circumferences

Transformation through investment in geometric shapes grouped elements can be of interest to use the investment as a tool for analysis in complex problems. In this case study transforming “beams circumferences corradicales” through various investments that transform. Later these transformations need to solve the problem “Apolonio” (circumference with three tangency constraints) o la “Generalization of the problem of Apollonius” (circumferences with three angular restrictions).

# The robustness of dynamic geometric constructions with Geogebra: Polar of a point of a circle

The study of the disciplines of classical geometry can be reinforced by using tools that allow constructions that can be changed dynamically: variational constructions.
The tool “Geogebra” It will serve to illustrate these concepts and demonstrate the importance of detailed knowledge of geometric relationships to ensure the robustness of the buildings we use in geometric reasoning, as, sometimes, some constructions may lose their validity.

# Triangle geometry [Problem]

We have seen in studying the concept of power or theorems Hick and height metric relations between segments.

In these relationships, along with the Pythagorean Theorem segments are related by quadratic forms that can also be interpreted as areas (product of two lengths)