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Conic Sections - Practice Questions & MCQ

Updated on Sep 18, 2023 18:34 AM | #JEE Main

Quick Facts

  • Introduction to Conic Section is considered one of the most asked concept.

  • 44 Questions around this concept.

Solve by difficulty

Which of the following is NOT a conic section ? 

What part is rotated about a fixed vertical axis in corating double napped cone?

What is the shape we get when we slice double napped cone parallel to x-y plane and not on vertex?

What is the limitations on the angle β ?

What happens when the plane cuts at an angle of β=90 but at the vertex ? 

Which conic do we get when β=35 and α=25 ?

What will happen if α=β=30 and we cut the double napped come with a plane?

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Let S1:x2+y2=9 and S2:(x2)2+y2=1. Then the locus of the centre of a variable circle S which touches S1 internally and S2 externally always passes through the points:

A conic section is teh locus of a point which moves in a plane so that its distance from fixed _______(1) is in a constant ratio to its perpendicular distance from a fixed ______(2)

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Match the column for the following figure

(i) PT                    (p) Subnormal

(ii) TM                   (q) tangent

(iii) PN                   (r) Normal

(iv) MN                  (r) Subtangent

 

 

Concepts Covered - 2

Introduction to Conic Section

Introduction to Conic Section

The two-dimensional curves that can be generated as cross-sections when a double cone is cut by a plane at different angles are called conic sections. 

We obtain different kinds of conic sections depending on the position of the intersecting plane concerning the cone and by the angle made by it with the vertical axis of the cone.

Let β be the angle made by the intersecting plane with the vertical axis of the cone.

For example, parabola, ellipse and hyperbola are conic sections as they are formed when a plane cuts a double cone as shown in the figure.

Note: a circle is a special case of ellipse when the plane is perpendicular to the axis of the double cone, and hence a circle is also a conic section

Definition of Conic Section in 2-dimensions

A conic section is the locus of a point which moves in a plane so that its distance from a fixed point is in a constant ratio to its perpendicular distance from a fixed line.

The fixed point is called the Focus of the conic and this fixed line is called the Directrix of the conic.

Also, the constant ratio is called the Eccentricity and is denoted by e.

From the figure

\\ {\;\;\;\;\;\;\;\;\;\;\;\;\;\frac{\mathrm{PS}}{\mathrm{PM}}=\text { constant }=\mathrm{e}}\\ \\ {\Rightarrow \;\;\;\;\;\;\;\;\;\;\;\mathrm{PS}=\mathrm{e} \cdot \mathrm{PM}}

Some Important Definitions to Remember

Axis: The straight line passing through the focus and perpendicular to the directrix is called the axis of the conic section.

Vertex: The point of intersection of the conic section and the axis is called the vertex of the conic section. 

Double ordinate: Any chord, which is perpendicular to the axis of the conic section, is called a double ordinate of the conic section. 

Focal chord: Any chord passing through the focus is called the focal chord of the conic section. 

Focal distance: The distance between the focus and any point on the conic is known as the focal distance of that point.

Latus rectum: Any chord passing through the focus and perpendicular to the axis is known as the latus rectum of the conic section. 

Centre: The point which bisects every chord of the conic passing through it, is called the centre of the conic section.

Equation of Conic Section:

The focus at S(h,k) and the Directrix : ax+by+c=0, then equation of conix

PS=ePM(xh)2+(yk)2=e|ax+by+c|a2+b2(xh)2+(yk)2=e2(ax+by+c)2a2+b2
 

Recognition of Conics

Recognition of Conics

Equation of conic represented by the general equation of second-degree

ax2+2hxy+by2+2gx+2fy+c=0
The discriminant of the above equation is denoted by Δ, where

Δ=abc+2fghaf2bg2ch2
It can also be written in determinant form as

|ahghbfgfc|
Case 1: When the focus lies on the directrix
Δ=0 : In this case, the equation represents a pair of straight lines

Case 2: When the focus does not lie on the directrix

\begin{array}{|c|c|}\hline \text { Conditions } & {\text { Nature of Conic }} \\ \hline \Delta \neq 0, h^{2}=a b & {\text { Parabola }} \\ \hline \Delta \neq 0, h^{2}<a b & {\text { Ellipse }} \\ \hline \Delta \neq 0, h^{2}>a b & {\text { Hyperbola }}\\ \hline\end{array}

Study it with Videos

Introduction to Conic Section
Recognition of Conics

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Books

Reference Books

Introduction to Conic Section

Mathematics for Joint Entrance Examination JEE (Advanced) : Coordinate Geometry

Page No. : 5.1

Line : 1

Recognition of Conics

Mathematics for Joint Entrance Examination JEE (Advanced) : Coordinate Geometry

Page No. : 5.1

Line : 40

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