Class XI · Chapter 10 · NCERT Mathematics

CHAPTER 10

Conic Sections

Curves Carved by the Cosmos

Circles, ellipses, parabolas, hyperbolas — nature's own curves, born from a single cone.

\(x²/a² + y²/b² = 1 (ellipse)\)
12 CBSE Marks
Difficulty
8 Topics
Very High JEE Weight

Topics Covered

8 key topics in this chapter

Circle: Standard & General Equation
Parabola: Standard Forms & Focus
Ellipse: Foci, Vertices, Eccentricity
Hyperbola: Asymptotes & Properties
Latus Rectum of Conics
Focal Chord Properties
Parametric Equations
Applications in Physics & Astronomy

Study Resources

𝑓 Key Formulae

Essential mathematical expressions for this chapter — understand derivations, not just results.

Circle
\[(x-h)^2+(y-k)^2=r^2\]
📌 Centre (h,k), radius r
Parabola (right)
\[y^2=4ax,\quad \text{focus }(a,0),\text{ directrix }x=-a\]
📌 a>0 opens right; a<0 opens left
Ellipse
\[\dfrac{x^2}{a^2}+\dfrac{y^2}{b^2}=1,\quad a>b\]
📌 c²=a²−b², e=c/a<1
Hyperbola
\[\dfrac{x^2}{a^2}-\dfrac{y^2}{b^2}=1\]
📌 c²=a²+b², e=c/a>1
Latus Rectum
\[\ell = \dfrac{2b^2}{a}\]
📌 For both ellipse and hyperbola
Eccentricity
\[e=0\text{(circle)},\;e<1\text{(ellipse)},\;e=1\text{(parabola)},\;e>1\text{(hyperbola)}\]
📌 Determines the conic type

🎯 Exam-Ready Insights

Important points to remember — curated from CBSE Board question patterns.

01

CBSE 6-mark: given an equation, identify the conic, find centre/focus/vertex/directrix/latus rectum — all five standard elements.

02

Always convert to standard form first by completing the square before finding parameters.

03

For parabola y²=4ax: focus=(a,0), vertex=(0,0), directrix: x=−a, latus rectum length=4a.

04

Ellipse: sum of focal distances = 2a (constant). Hyperbola: difference = 2a.

05

Eccentricity classifies the conic — memorise e=0,<1,=1,>1 for circle, ellipse, parabola, hyperbola.

🏆 Competitive Exam Strategy

Targeted tips for JEE Main, JEE Advanced, NEET, BITSAT, and KVPY.

JEE Main

JEE Main conics questions are high-scorers — the ellipse and hyperbola each get 1–2 problems. Focus on foci, normals, and tangents.

JEE Advanced

JEE Advanced tests intersection of conics, chord of contact, and parametric equations — essential for full marks.

NEET

NEET uses elliptical orbits (Kepler's laws) — understanding that planets trace ellipses with the Sun at one focus is conceptually tested.

BITSAT

BITSAT rapidfire: match each equation to its conic type by comparing signs and denominators.

⚠️ Common Mistakes to Avoid

Confusing major and minor axes when a < b in the ellipse equation.

Taking e = a/c instead of e = c/a — eccentricity is always c/a.

Not completing the square when the conic is given in general form.

Mixing up parabola openings: y²=4ax opens rightward; x²=4ay opens upward.

💡 Key Takeaways

All conics are cross-sections of a double cone at different angles.

Standard forms must be memorised — completing the square converts any conic to standard form.

Eccentricity e is the single number that identifies a conic type.

Latus rectum = chord through focus perpendicular to the axis; length = 2b²/a for ellipse/hyperbola.

Parametric forms: Circle (cosθ,sinθ), Ellipse (acosθ,bsinθ), Parabola (at²,2at).

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