Introduction to Hyperbola
A hyperbola is the locus of a point that moves in a plane so that the ratio of its distance from a fixed point (the focus) to its distance from a fixed line (the directrix) is a constant . Its standard equation is , where . This page explains every basic term of the hyperbola, including eccentricity, foci, directrices, axes, vertices and latus rectum, along with the conjugate hyperbola, auxiliary circle, parametric form and position of a point, with solved examples for JEE Main and JEE Advanced.
- Standard equation: , with
- Eccentricity: , always
- Foci ; directrices ; vertices
- Transverse axis ; conjugate axis
- Latus rectum ; its ends are
- Focal distances: , , so
- Conjugate hyperbola ; if are the two eccentricities,
- Auxiliary circle ; parametric point
- Position of : is (inside), (on), (outside)
1. Definition of a Hyperbola
Hyperbolic curves are of special importance in science and technology, especially in astronomy and space studies. For example, a body that passes the Sun only once, without being captured into orbit, moves along a hyperbolic path. In this chapter we study the characteristics of such curves.
Definition: A hyperbola is the locus of a point moving in a plane such that the ratio of its distance from a fixed point to its distance from a fixed line is a constant greater than 1. The fixed point (focus) does not lie on the fixed line (directrix).
Hyperbola as a conic section
A hyperbola is one of the conic sections, the curves obtained when a plane cuts a right circular double cone. Let be the semi-vertical angle of the cone and the angle between the cutting plane and the axis of the cone. When , the plane cuts both nappes of the cone and the section is a hyperbola.
| Angle between plane and axis | Section obtained |
|---|---|
| Circle | |
| Ellipse | |
| Parabola | |
| Hyperbola |
2. Standard Equation of a Hyperbola
Take the focus as and the directrix as , where . For any point on the curve, , and the definition gives
Standard equation of a hyperbola:
Because the equation contains only even powers of and , the curve is symmetric about both axes. So and act as a second focus and a second directrix.
Basic terms of the hyperbola
| Term | Meaning | For |
|---|---|---|
| Eccentricity | The constant ratio , always greater than 1 | |
| Foci | The two fixed points | and |
| Directrices | The fixed lines, one for each focus | and |
| Transverse axis | The line segment of length on which both foci and lie | Along the -axis, length |
| Conjugate axis | The line segment of length between and | Along the -axis, length |
| Principal axes | The transverse and conjugate axes taken together | The -axis and -axis |
| Vertices | Points where the hyperbola meets its transverse axis | and |
| Centre | The point that bisects every chord of the conic drawn through it | |
| Focal chord | A chord that passes through a focus | Any chord through or |
| Double ordinate | A chord perpendicular to the transverse axis | A chord parallel to the -axis |
| Latus rectum | A focal chord perpendicular to the transverse axis | Lies on , length |
Length of the latus rectum
Putting in the equation gives , so . Hence the length of the latus rectum is
Note:
- (i) Length of latus rectum (distance of the focus from the corresponding directrix). Here the distance is .
- (ii) The end points of the latera recta are , , and .
General note: The fundamental equation of a hyperbola differs from that of an ellipse only in having in place of . So many propositions for the hyperbola can be obtained from those for the ellipse simply by changing the sign of .
Focal distances of a point
For a point on the right branch, for the directrix . Using for each focus-directrix pair:
So . On the left branch the roles swap and . In both cases
This gives an equivalent definition: a hyperbola is the locus of a point whose distances from two fixed points (the foci) differ by a constant.
Let be any point on the hyperbola and draw perpendicular from to the directrix. By definition, , so .
This is the required hyperbola: .
Let the hyperbola be . Then transverse axis and latus rectum . According to the question,
Hence the required eccentricity is .
3. Hyperbola with Centre at
When the centre is shifted to and the axes stay parallel to the coordinate axes, replace by and by . All the results of the standard form carry over after this shift.
| Property | ||
|---|---|---|
| Centre | ||
| Transverse axis | Along , length | Along , length |
| Vertices | ||
| Foci | ||
| Directrices | ||
| Eccentricity | ||
| Latus rectum |
4. Conjugate Hyperbola
Two hyperbolas such that the transverse and conjugate axes of one are respectively the conjugate and transverse axes of the other are called conjugate hyperbolas of each other.
For the conjugate hyperbola the transverse axis lies along the -axis, so the roles of and are exchanged:
| Property | Hyperbola | Conjugate |
|---|---|---|
| Transverse axis | , along -axis | , along -axis |
| Conjugate axis | , along -axis | , along -axis |
| Relation | ||
| Eccentricity | ||
| Vertices | ||
| Foci | ||
| Directrices | ||
| Latus rectum |
Note:
- (a) If and are the eccentricities of a hyperbola and its conjugate, then . This follows because and .
- (b) The foci of a hyperbola and its conjugate are concyclic and form the vertices of a square. All four foci are at distance from the centre.
- (c) Two hyperbolas are said to be similar if they have the same eccentricity.
- (d) Two similar hyperbolas are said to be equal if they have the same latus rectum.
- (e) If a hyperbola is equilateral, then its conjugate hyperbola is also equilateral.
Dividing by 144, the equation becomes , which is of the form (a conjugate-type hyperbola). So , giving .
- Length of transverse axis:
- Length of conjugate axis:
- Eccentricity:
- Foci: , that is,
- Vertices: , that is,
- Length of latus rectum:
- Directrices: , that is,
5. Auxiliary Circle
The circle drawn with centre and the transverse axis as diameter is called the auxiliary circle of the hyperbola. For its equation is
In the figure below, is the foot of the ordinate of a point on the hyperbola and is a tangent to the auxiliary circle. The points and are called the corresponding points of the hyperbola and the auxiliary circle. Since and , we get where .
6. Parametric Representation
The equations and together represent the hyperbola , where is a parameter.
This works because . Values give the right branch and give the left branch.
Note: If is on the hyperbola, then its corresponding point is on the auxiliary circle. The angle is called the eccentric angle of .
7. Position of a Point with Respect to a Hyperbola
For the point , the quantity
is positive, zero or negative according as the point lies inside, on or outside the hyperbola. Here "inside" means the region between a branch and its focus.
Here .
So the point lies inside the hyperbola .
8. Practice Problems
- Find the equation of the hyperbola whose foci are and and eccentricity is 2.
Answer: - Obtain the equation of a hyperbola with the coordinate axes as principal axes, given that the distances of one of its vertices from the foci are 9 and 1 units.
Answer: or - The foci of a hyperbola coincide with the foci of the ellipse . Find the equation of the hyperbola if its eccentricity is 2.
Answer:
Common Mistakes to Avoid
- Using the ellipse relation . For a hyperbola it is , so is always greater than 1.
- Assuming . In a hyperbola can be smaller than, equal to or larger than . The transverse axis is decided by which squared term is positive, not by which denominator is larger.
- For , taking the transverse axis as . The right-hand side is , so the transverse axis is along the -axis with length .
- Writing for a hyperbola and its conjugate. The correct relation is .
- Reading as "outside". For a hyperbola, means the point lies inside, in the region containing a focus. This is the opposite sign convention to the ellipse.
- Using as the parametric point. That belongs to the ellipse; the hyperbola uses .
- Forgetting to add the centre in a shifted hyperbola: the foci of are , not .
Frequently Asked Questions
What is a hyperbola in coordinate geometry?
A hyperbola is the locus of a point whose distance from a fixed point (focus) bears a constant ratio to its distance from a fixed line (directrix). Equivalently, the difference of its distances from the two foci is constant and equal to . Its standard equation is .
How do you find the eccentricity of a hyperbola?
For , use , where is the semi-transverse axis. For the conjugate form , use . The value always exceeds 1, and it equals when .
What is the difference between the transverse axis and the conjugate axis?
The transverse axis is the segment joining the two vertices; both foci lie on its line and its length is for . The conjugate axis is the perpendicular segment through the centre joining , with length . The curve never meets its conjugate axis.
What is the length of the latus rectum of a hyperbola?
The latus rectum is the focal chord perpendicular to the transverse axis. For its length is , which also equals and the square of the conjugate axis divided by the transverse axis. Its end points are .
What is a conjugate hyperbola?
The conjugate of is , whose transverse and conjugate axes are swapped. Both share the same centre and asymptotes, their four foci form a square, and their eccentricities satisfy .
Why does a hyperbola use sec and tan in its parametric form?
Substituting and into gives , so every value of gives a point on the curve. Geometrically, is the angle at the centre to the corresponding point on the auxiliary circle.
Is the hyperbola in the JEE Main syllabus?
Yes. The JEE Main syllabus includes equations of the parabola, ellipse and hyperbola in standard form, and questions on eccentricity, foci, latus rectum and the conjugate hyperbola are common. Every result on this page is directly usable in JEE Main problems.
Which basic hyperbola results matter most for JEE Advanced?
JEE Advanced lists foci, directrices, eccentricity and parametric equations of the hyperbola, followed by tangents, normals and locus problems. Be fluent with , the focal distance property , the parametric point and the sign of , since multi-step problems build on them.
Previous year questions on Introduction to Hyperbola
24 questions from past papers, each with a step-by-step solution.
- JEE Main 2026 Apr 2 Shift 2, Mathematics Q11
- JEE Main 2026 Apr 4 Shift 2, Mathematics Q11
- JEE Main 2026 Apr 5 Shift 2, Mathematics Q13
- JEE Main 2026 Apr 6 Shift 1, Mathematics Q11
- JEE Main 2026 Apr 6 Shift 2, Mathematics Q11
- JEE Main 2026 Jan 21 Shift 1, Mathematics Q11
- JEE Main 2026 Jan 22 Shift 1, Mathematics Q10
- JEE Main 2026 Jan 22 Shift 2, Mathematics Q11
- JEE Main 2026 Jan 23 Shift 1, Mathematics Q1
- JEE Main 2026 Jan 23 Shift 2, Mathematics Q9
Show all 24 questions
- JEE Main 2026 Jan 28 Shift 1, Mathematics Q22
- JEE Main 2026 Jan 28 Shift 2, Mathematics Q10
- JEE Advanced 2026 Paper 2, Mathematics Section 3 Q4
- JEE Main 2025 Apr 2 Shift 1, Mathematics Q2
- JEE Main 2025 Apr 3 Shift 1, Mathematics Q22
- JEE Main 2025 Apr 3 Shift 2, Mathematics Q25
- JEE Main 2025 Apr 4 Shift 2, Mathematics Q10
- JEE Main 2025 Apr 7 Shift 1, Mathematics Q23
- JEE Main 2025 Apr 7 Shift 2, Mathematics Q24
- JEE Main 2025 Jan 22 Shift 1, Mathematics Q20
- JEE Main 2025 Jan 24 Shift 2, Mathematics Q24
- JEE Main 2025 Jan 28 Shift 2, Mathematics Q19
- JEE Advanced 2025 Paper 2, Mathematics Section 1 Q4
- JEE Advanced 2022 Paper 2, Mathematics Section 1 Q7
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