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.

6689 questions
5
votes
1 answer

Equation of Angle Bisectors for a Pair of Straight Lines passing through the Origin

Suppose you have a pair of lines passing through origin, $ax^2 + 2hxy +by^2 = 0$, how would you find the equation of pair of angle bisectors for this pair of lines. I can do this for $2$ separate lines, but I am not able to figure it out for a pair…
user34304
  • 2,749
5
votes
4 answers

Parametric equation for a plane perpendicular to a vector

The implicit equation for a plane perpendicular to a given vector at the origin is $ax + by + cz = 0$. I can write this in parametric form as $x = t, y = u, z = -\frac{at + bu}{c}$. The only problem is that I can't use this equation when $c = 0$,…
jnm2
  • 3,170
5
votes
2 answers

Circumcircle in 3D

The vertices of a triangle are given as $A(1, 0, 0), B(3, 1, 0), C(5, 2, 1) $. Find the center and the radius of the circumcircle of this triangle. My Attempt: The normal to the plane of the triangle is $ N = (B - A) \times (C - A) \\ = ( (3, 1,…
Hosam Hajeer
  • 21,978
5
votes
1 answer

How to calculate the area closed by a parabola and a line without calculus?

In order to simplify the problem, suppose we have a parabola $y=ax^2+bx+c$, here $a\neq0$, and a line $y=kx+d$, here $k\neq0$. We can assume that they will intersect at two different points. Thus, the $\Delta$ of the equation $ax^2+bx+c=kx+d$ will…
string
  • 743
5
votes
1 answer

ABC is a triangle, right-angled at B. And it is inscribed in the parabola $y^2=4x$. Find the minimum length of AC.

We have a right-angled triangle inscribed in the parabola $y^2=4x$ and we have to find the minimum length of its hypotenuse. Taking the points as $A((t_1)^2,2t_1)$, $B((t_2)^2,2t_2)$ and $C((t_3)^2,2t_3)$. We know that $\overrightarrow{AB}$ is…
5
votes
3 answers

A simple(?) Analytical Geometry Question (Ellipse) my teacher can't solve

Here's the story: I am a high school student who absolutely loves math. So I took a university level mathematics course that is renowned throughout our school for being extremely rigorous and tough. Last week we had our first lesson, and this…
5
votes
2 answers

Average projected area of an ellipsoid

Consider an ellipsoid of semi-axes a, b, c (possibly prolate, b=c). I am interested in the "shadow" of this solid onto a distant plane, in a given direction d=(k,l,m) orthogonal to that plane. By shadow I mean the projected area onto the plane: each…
baptiste
  • 153
5
votes
2 answers

If line through point $P(a,2)$ meets the ellipse $\frac{x^2}{9}+\frac{y^2}{4}=1$ at A and D and meets the coordinate axis at B and C

If line through point $P(a,2)$ meets the ellipse $\frac{x^2}{9}+\frac{y^2}{4}=1$ at $A$ and $D$ and meets the coordinate axes at $B$ and $C$ so that $PA$, $PB$, $PC$, $PD$ are in geometric progression, then the possible values of $a$ can…
Vinod Kumar Punia
  • 5,648
  • 2
  • 41
  • 96
5
votes
0 answers

A nice formula for area of the triangle

The following problem can be found in S.L. Loney's The Elements of Coordinate Geometry (Examples X, Problem 19): Prove that the if the area of the triangle formed by the three straight lines $a_1x+b_1y+c_1=0, a_2x+b_2y+c_2=0, a_3x+b_3y+c_3=0$ is…
Isomorphism
  • 5,693
5
votes
1 answer

Find the condition on $a$ and $b$ so that the two tangents drawn to the parabola $y^2=4ax$ from a point are normals to the parabola $x^2=4by$

Find the condition on $a$ and $b$ so that the two tangents drawn to the parabola $y^2=4ax$ from a point are normals to the parabola $x^2=4by.$ The required condition is $a^2>8b^2$.I dont know how to prove it.I tried. Let $(h,k)$ be the point from…
Brahmagupta
  • 4,204
4
votes
2 answers

Altitudes of a triangle are concurrent (using co-ordinate geometry)

I need to prove that the altitudes of a triangle intersect at a given point using co-ordinate geometry. I am thinking of assuming that point to be $(x,y)$ and then using slope equations to prove that the point exists and I can think of another…
Ishaan Singh
  • 1,025
4
votes
2 answers

assessing linear relationships as logarithms

I am teaching myself maths. I am not sure how to approach this problem. It is assessing linear relationships of the form $y=mx+c$ as logarithms. Here I have gotten as far as taking the gradient ($\log e$) of $\log \frac{s}{t} = -0.6363...$ so $e =…
4
votes
2 answers

"Looping" equation

I'm looking for a equation that describes the shape of a "Looping" in the best way. I really don't know how to start here, as it isn't even a function (if it were, I could just use spline interpolation), so do you have any idea on how to best…
vauge
  • 323
4
votes
2 answers

Question straight from the SAT

If a coordinate system is devised so that the positive y-axis makes an angle of 60 degrees with the positive x-axis, what is the distance between the points with coordinates (4,-3) and (5,1)? I'm sure you guys can get it without the multiple choice…
4
votes
2 answers

Find the point of intersection of the straight line $\frac{X+1}{4}=\frac{Y-2}{-2}=\frac{Z+6}{7}$ and plane $3X+8Y-9Z=0$

Find the point of intersection of the straight line $$\frac{X+1}{4}=\frac{Y-2}{-2}=\frac{Z+6}{7}$$ and plane $3X+8Y-9Z=0$ the point of the line is $M(-1,2,-6)$ and direction vector of the line is $A(4,-2,7)$ I would like to get some advice how to…
Ofir Attia
  • 3,136
1
2
3
68 69