Questions tagged [analytic-geometry]

Questions on the use of algebraic techniques for proving geometric facts. Analytic Geometry is a branch of algebra that is used to model geometric objects - points, (straight) lines, and circles being the most basic of these. It is concerned with defining and representing geometrical shapes in a numerical way.

Analytic geometry, also called coordinate geometry, mathematical subject in which algebraic symbolism and methods are used to represent and solve problems in geometry.

The importance of analytic geometry is that it establishes a correspondence between geometric curves and algebraic equations. This correspondence makes it possible to reformulate problems in geometry as equivalent problems in algebra, and vice versa; the methods of either subject can then be used to solve problems in the other.

Analytic geometry was introduced by René Descartes in $1637$ and was of fundamental importance in the development of the calculus by Sir Isaac Newton and G. W. Leibniz in the late $17^{th}$ cent. More recently it has served as the basis for the modern development and exploitation of algebraic geometry.

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Find the equation of a circle that intersects the $y$-axis at the origin and at the point $(0,6)$ and also touches the $x$ axis. - basic question

Find the equation of a circle that intersects the $y$-axis at the origin and at the point $(0,6)$ and also touches the $x$ axis. Okay, so I wasn't sure how to do this so I looked at the answer at the back of the book and decided to graph it. The…
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Using substitution to determine if a given point is on the line

Is it necessary to rearrange the equation of a line so that it is in the $y=mx+b$ form before using substitution to check whether a point is on the line? If yes, why? If no, why?
Lucille
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Why does the area of an area element increase by $1/cos(\theta)$ after tilting it?

While reading this chapter of the Feynman Lectures I came across a statement I didn't know how to prove. He mentions below Eq. 4.30 that when you take a surface and tilt it by some angle $\theta$, the area of the new surface is increased by a factor…
m009
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How to compute point from {length and angle}

How to compute point from {length and angle}?
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How can I find the coordinates of a point which is the reflection of a point about a line in 3D

I am currently working on a project on Matlab and I need to find the coordinates of a point which is reflected about a line. I know how to do it in 2D but in 3D things are getting ugly. So, we have a line which goes through two points $A(x_1, y_1,…
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Proving Coplanarity of 3 vectors

Let $a,b,c$ be three vectors such that $|a|=|b|=|c|=\sqrt{2} $ and $a\cdot b = b\cdot c = a\cdot c = -1 $ . How can I prove that they are all coplanar? I found that the angle between every two of them is $120 $ degrees, and tried to use this in…
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Unicursal Curve Double Points

To quote Goursat: It is shown in treatises on Analytic Geometry that every unicursal curve of degree n has $\frac{(n-1)(n-2)}{2}$ double points, and, conversely, that every curve of degree n which has this number of double points is…
bolbteppa
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Proving the following is a Group

I'm studying this weird course called "Analytic Geometry", but in reality it seems like a mash of modern or abstract Algebra (...I'm not so sure...), and includes stuff like Affine transformations, isomorphism, quadrics etc'. It's a really weird…
oey
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Finding the point of concurrence of a family of straight lines

If $6a^2-3b^2-c^2+7ab-ac+4bc=0$, then the family of lines $ax+by+c=0$ is concurrent at $(-2,-3)$ $(3,-1)$ $(2,3)$ $(-3,1)$ Multiple answers are possible. I am not able to group terms of the expression $6a^2-3b^2-c^2+7ab-ac+4bc=0$ so as to get…
Tejas
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Sequence of coordinates on a polygon

If we have all coordinates of the vertices of an arbitrary polyhedron, is it possible to determine on what faces they are and in what order? Actually, I already know the first part of the question, because I did it using linear programming.…
user110696
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Intersection of curve and line

This is a question which I want to solve, taken from this sample question paper for an exam I'm appearing for tommorow: If a line, parallel to, but not identical with, x- axis cuts the graph of the curve $$y={(x-1)}/({(x-2)(x-3)})$$ at $x=a$ and…
A Googler
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Easier way to calculate this point besides line intersection?

Given are all points except E, plus |AF| = |DC|. Considering that the lines AB and FE, as well as BC and ED are parallel, is there an easier way to calculate E? Maybe some relation with B? I'd like to express the coordinates from E as short as…
Clash
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If $l(x,y)=0$ and $l'(x,y)=0$ intersects in $P_0(x_0,y_0)$ then $ \lambda l (x,y) + \lambda ' l'(x,y)=0 , \quad ( \lambda +\lambda ' =1 )$

I'm reading "What is Mathematics?" and found this question. let $l(x,y)=0$ represents the equation $ax+by+c=0$ of a line $l$,and so does $l'(x,y)=0$ . now let $\lambda + \lambda ' =1 $. Show that, if $l$ and $l'$ intersect in $P_0(x_0,y_0)$,then…
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Simple analytic geometry - calculate the point coordinates

I have the coordinates from A and B and the distance d. How can I calculate the point C? If the triangle wasn't tilted, it'd be peace of cake. Actually, why is it easier if the triangle isn't tilted? (Don't worry about this question though) I can…
Clash
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Finding the locus of the third vertex of the triangle under the given conditions

A triangle is circumscribed to the ellipse $\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$ and two of its vertices lie on the directrices, such that one lies on each directrix. Then, the locus of the third vertex of the triangle is? I tried using an affine…