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 the lines of intersection of the plane $x - 3y + z = 0$ and the cone $x^2 - 5y^2 + z^2 = 0$

I have the two equations $$l - 3m + n = 0$$ and $$l^2 - 5m^2 + n^2 = 0$$ and from here I am lost on how to proceed. I tried substituting l or m or n into the lower equation but keep getting stumped. (Because I get a double variable, i.e. $mn$, $ln$,…
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Find a plane M such that $l_1\in M (l_1$ is contained in $M$), and $M$ is parallel $l_2$.

$l_{1} : \left\lbrace \begin{array}{lcl} 2 x + 3 y + 4 z = 7 && \mbox{ } \\ 4 x + y - 2 z = -1 && \mbox{ } \\ \end{array} \right.$ $l_{2} : \frac{x-2}{20}=\frac{y-2}{10}=\frac{z +1 }{5}$ I have to find a plane M such that $l_1\in M (l_1$ is…
Algo
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Find the equation of a line

Find the equation of the line through (12/5 , 1), forming with the axes a triangle area of 5. There are 4 solutions and how can i get it?
Ziiyo
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Computing $r$ for a $1\times r$ strip inside (cut from) a $1\times (1-r)$ rectangle

Cut a $1\times r$ strip from a $1\times 1$ square and place it inside the remaining $1\times (1-r)$ rectangle such that every corner of the strip touches the interior of a different side of the rectangle. Compute $r$. I tried to solve this problem…
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Equation of a line that intersects two lines in a segment of length $2$

How can I find the line that passes through the point $(1,1)$ and intersects the lines $x+y=0$ and $x-y-1=0$ in a segment of length $2$? I've tried assuming that we know the points of the intersections and then find the conditions, but an equation…
Labi
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Find the volume of B given an equation for A

We define a solid A by: $$\frac{19}{x^2} + \frac{14}{y^2} \leq z^4 \quad (0 \leq z \leq 1)$$ We define a solid B by: $$x^2 + y^2 \leq z^4 \quad (0 \leq z \leq 1)$$ The volume of the solid B is ? Please don't tell me the answer, just guide/tell me…
Carlos
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P is a point of the segment AB $\iff \vec{CP} = \alpha \vec{CA} + \beta \vec{CB}$

I am trying to prove the following statement: P is a point of the segment AB $\iff \vec{CP} = \alpha \vec{CA} + \beta \vec{CB}$ where $A,B,C$ are arbitrary points, with $A \neq B$ , and $\alpha, \beta > 0$, $\alpha + \beta = 1$. Using the following…
Montresor
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Proving a triangle is a right triangle given vertices, using vector dot product

I want to to show that this triangle is a right triangle. I know that the dot of the vectors need to be $0.$ I tried to dot between them but I don't get zero. Claim: Triangle $\bigtriangleup MNP,\;\;\,M(1,-2,3),\;\;N(0,0,4),\;\; P(4,2,-2)\;$ is a…
Ofir Attia
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A proof in circles

The question is this: Show that the equation of a straight line meeting the circle $ x^2 + y^2 = a^2 $ in two points at equal distances $d$ from a point $(m, n)$ on its circumference is $ mx + ny - a^2 + \dfrac {d^2} {2} $ I am confused. Hints…
Parth Thakkar
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Coordinate geometry, finding the locus of a point. Is the solution in the text book incorrect?

I spent some time on this question earlier today - the most difficult part was understanding the language used in the question and being able to visualise the point stated in the question as a point in the plane. After some wrestling I have managed…
GR L
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How did I get the answer right using this method?

$A(1,4),$ $B(2,3)$ are the vertices of $\triangle ABC$. Centroid of the triangle lies on the locus $3x-9y+13=0$. If the equation of the locus of the third vertex $C$ is $x-by-c=0$ then find $(b+c)$. My Solution - Let $C\equiv (h,k) ⇒ G\equiv…
Aleph
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Equation of the ellipse between 2 points (its vertices)

The idea is to start drawing an ellipse where the mouse is clicked (first vertex of the major axis) and ends at the mouse pointer (second vertex of the major axis). This way you could draw ellipses to where you move the mouse and with the desired…
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Find the foot of the perpendicular through the point $A(-3;2)$ to the line $2x-y+4=0$.

Find the foot of the perpendicular through the point $A(-3;2)$ to the line $2x-y+4=0$. Let $AH\perp a:2x-y+4=0, H\in a.$ I have tried to use the fact that the vector $\vec{AH}(x_H+3;y_H-2)$ is a normal vector of the line $a$ and also $a$ passes…
mat1
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finding parabola equation

The centers of all circles which tangent to a circle $P(2R,0)$ with radius $R$ and to the line $x=-t$ is a Canonical parabola. Need to find the equation of that parabola and $t$ (by $R$). so: \begin{align}&\sqrt{{{(x-2R)}^{2}}+{{y}^{2}}}=R+\left|…
asker
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Origin point of a normal vector to a given point, from a given plane

I have a plane $P: 2x + y - z -1 = 0.$ I have a point $A_1( 0, 1, 1).$ Question asks to find the coordinates of $A_2$, which is symetrical to $A_1$ with respect to $P$. I tried using the formula for distance between a point and a plane(for $A_1$ and…
Midaga
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