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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Why is the equation $z=(x+y)^2+y^2$ a paraboloid?

Why is the equation $z=(x+y)^2+y^2$ a paraboloid?, as the right side is expanded, it is $z=x^2+2xy+2y^2$. The equation of a paraboloid in some sources is simply $z=\frac{x^2}{a^2}+\frac{y^2}{b^2}$ and there is no the product of $x$ and $y$ in the…
wawar05
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Not being able to understand intersection of two cones.

I do understand that when a plane cuts a cone it does in two lines, but where did the other two lines come from? The solution(see pic) says that "the two cones intersect in four lines", now how is that possible? It should have been two lines as a…
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Intersection Point of a Line and four Planes

Let's assume a helicopter crashes into a wall after flying in a straight line: $$g : \overrightarrow {OX} = \begin{pmatrix}2\\5\\28 \end{pmatrix}+ \lambda*\begin{pmatrix}1\\\frac{1}{3}\\\frac{-1}{11} \end{pmatrix} $$ There are four walls which form…
libjup
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Show that the locus of $P$ as $t$ varies is a circle .

A line through the point $(1,0)$ meets the variable line $y=tx$ at right angle at point $P.$ Find in terms of $t$,the coordinates of $P.$ I’ve found the coordinates of $P$ to be $\displaystyle\Big(\frac{1}{1+t^2},\frac{t}{1+t^2}\Big)$ Show that…
gc3941d
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Prove that the midpoint of PQ lies on the straight line $y+r^2x=0$.

Prove that the equation of the chord joining the points $P(cp,\displaystyle\frac{c}{p})$ and $Q(cq,\displaystyle\frac{c}{q})$ on the rectangular hyperbola $xy=c^2$ is $pqy+x=c(p+q)$. So, I've found that the gradient of the chord $PQ$ is…
gc3941d
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Equations of the points

In an orthonormal system of coordinates we consider the points A(2, 0) and B(0, 1) and two “moving” points: P (x, 0) Q(0, −3x) with x < 0. Consider now the set of all points obtained by intersecting the straight lines PB and QA. Find the equation of…
Lao
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A "jeopardy" with common tangents of two hyperbolas

Please do not overlook the pre-degree mathematics, there can be some un-noticed avenues/issues. For the hyperbola $H=x^2/a^2-y^2/b^2=1$, the equation of tangents is $T:y=mx\pm\sqrt{a^2m^2-b^2}$. Among conics the hyperbola has four distinctions:…
Z Ahmed
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What is the transformation set?

Suppose I have the following triangle in $\mathbb{R}^2$, $ A = \{ (x,y) \, | \, 0 \leq y \leq x \leq 1 \}$. I now perform the coordinate transformation $ z = \frac{y}{x}, u= x $. I now want to express the set $A$ as coordinates $(u,z)$, thus $ A =…
PROB123
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Given two points A and B, how do you find Y according to X?

I have two points $ A = (3,5)$ and $B = (5,2)$, I want to find their midpoint C = (4, Y). In this case Y would be 3.5 Is there a formula to find out what the $ Y $ of a point is, in relation to the other two points? exemple: Given A (3.5) B (5.2)…
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Equation of circumcircle of a triangle which has minimum area

From a point $ P(0,b) $ two tangents are drawn to the circle $ x^2+y^2=16 $ and these two tangents intersect x-axis at two points A and B .If the area of triangle PAB is minimum ,then prove that the equation of its circumcircle is $ x^2+y^2=32…
Normal
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Help me with finding the equation of the Plane containing the points: p=(2,1,3), q=(1,0,1) and r=(2,-1,1).

Given three points p=(2,1,3), q=(1,0,1) and r=(2,-1,1), find the Cartesian equation of the plane containing those points.
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How could you describe a straight vertical line in terms of y?

I asked my Calculus Teacher this and he had no answer, we were talking about linear equations just to brush up on grade 12 maths and I never thought to ask but is it at all possible to describe an equation like x=3 in terms of y? There is no y term…
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Find the locus of centroid of right angled isoceles triangle for the following given data.

An isosceles right angled triangle whose sides are $1, 1, \sqrt{2}$ lies entirely in the first quadrant with the ends of the hypotenuse on the coordinate axes. If it slides prove that the locus of its centroid is $(3x-y)^2 + (x-3y)^2…
prat
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Plane equation through point perpendicular to line.

I must write an equation for plane which goes through point $B(2; -3; 1)$ perpendicular to line $ \left\{ \begin{array}{c} x=2t-1 \\ y=7-3t \\ z=0 \end{array} \right. $ From that I obtain line direction vector (normal vector of line?) $v=(2; -3;…
Arnie
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If the point $(a,a)$ falls between the lines $|x+y|=2$ then prove that $|a|<1$

The lines are $$x+y=2$$ $$x+y=-2$$ This question is very easy to solve using a graph, but is there a way to solve it mathematically, ie. without any drawning, because it’s not always possible to draw a graph.
Aditya
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