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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Equation of a line making equal and positive intercepts

Q. Find the equation of line passing through the pt of intersection of the lines- $3x-y=5$ and $x+3y=1$ and making equal and positive intercepts on both the axes. A. To find the pt of intersection substitute $x=1-3y$ in $3x-y=5$. Thus, $y=…
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figuring out the sum of angles from the addition of geometrical shapes within a circle

if you add a number with another you get the sum of the two.(1+1=2, 2+2=4) right? but if you take a circle and put a horizontal line through it you have 4 angles in it. put another circle with a vertical line through it together with the other you…
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locus of orthocentre of given triangle if $\tan B+\tan C = c$

Vertex $A$ of $\triangle ABC$ moves in such a way that $\tan B+\tan C = c(\bf{constant}),$ Then locus of orthocentre of $\triangle ABC$ is ( side $BC$ is fixed) $\bf{My\; Try::}$ We can write $$\tan B+\tan C = c\Rightarrow \frac{\sin B}{\cos…
juantheron
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Finding slope of a line given angle it makes with a line of a given slope

Given the slope of a line and the angle it makes with another line, how to find the slope of the other line?
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Prove this equation represents a pair of straight lines.

I am to prove that $(ab-h^2)(ax^2+2hxy+by^2+2gx+2fy)+af^2+bg^2-2fgh=0$ represents a pair of straight lines. I am aware of the condition that is represents a pair of straight lines if $abc+2fgh-af^2-bg^2-ch^2=0$ in the general equation for 2nd…
Ayan Shah
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Find the equations of the common tangents to the parabola $y^2=15x$ and the circle $x^2+y^2=16$.

The text says: Find the equations of the common tangents to the parabola $y^2=15x$ and the circle $x^2+y^2=16$. I tried the approach of the discriminant and also one using the distance from a line but both didn't work for me. A previous exercise…
Phil
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Equation of tangent to a circle

Find an equation of the tangent to the circle with equation $x^2+y^2-10x+4y+4=0$ at the point $(2,2)$ I have solved up to $4y - 8 = 3x - 6$, but I am not sure whether the final answer should be $3x-4y+2=0$ OR whether it should be…
Dan
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How to get the equation of a circle with the given information

You have a center of a circle $M(-2,3)$ going through a point $P(1,7)$. What is the equation of the circle? I thought you could solve it by $R^2 = 3^2 + 4^2$, but that would just give a radius of 5 because there aren't any $x$ or $y$'s. Then I…
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Closed-form condition for concyclicity

$A_i(x_i, y_i)$, where $i=0,1,2,3$, are four points such that no three of them are collinear. Is there a closed form on the condition that they are concyclic? Answers with $x_0 = y_0 = x_1 (\text { or } y_1) = 0$ are also welcome.
Mick
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Find the equation of two ...

Find the single equation of two straight lines that pass through the point $(2,3)$ and parallel to the line $x^2 - 6xy + 8y^2 = 0$. My Attempt: Let, $a_1x+b_1y=0$ and $a_2x+b_2y=0$ be the two lines represented by…
pi-π
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The eqn $ax^2+2hxy+by^2........$

The equation $$ax^2+2hxy+by^2+2gx+2fy+c=0$$ represents a pair of parallel lines. Prove that the equation of the line mid way between the two parallel lines us $hx+by+f=0$ My Attempt: Let the lines be $lx+my+n_1=0$ and…
pi-π
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Find the ratio in which the perpendicular

Find the ratio in which the perpendicular from $(4,1)$ to the line segment joining the points $(2,-1)$ and $(6,1)$ divides the segment. My Approach: Equation of the line joining the points $(2,-1)$ and $(6,1)$ is given by: $$y-y_1=\frac…
pi-π
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If the chord $x+y=b$ of the curve ...

If the chord $x+y=b$ of the curve $x^2+y^2-2ax-4a^2=0$ subtends a right angle at the origin, prove that: $b(b-a)=4a^2$ My Approach. Given, Equation of the chord, $$x+y=b$$ $$\frac {x+y}{b}=1$$ Now, Equation of the…
pi-π
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All "pixels" touched by line segment

Say you have a line segment somewhere on the Cartesian plane that connects the points $(x_1,y_1)$ and $(x_2,y_2)$, and there are "pixels". For simplicity's sake, let's say that the pixels are 1 unit by 1 unit. How could I go about finding all the…
Polygon
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Proving that a given line is tangent to a hyperbola

The question is: a line $x \cos\theta + y\sin\theta = p$ is given such that $a^2\cos^2\theta - b^2\sin^2\theta =p^2$. I have to prove that it touches a hyperbola $\frac{x^2}{a^2} - \frac{y^2}{b^2} = 1$. I do not see how to proceed. I thought I…