LEARN · EXPLAIN · REVISE

Find the eccentricity.

Read the idea, work independently, then explain what changed.

高二選擇性必修第一册(A版).pdf · 3.2 · PDF 123 / printed page 118

Revisit first: Ellipse

TOPIC 01

Hyperbola

Use the distance-difference definition, asymptotes and branch restrictions.

Use one hint at a time. A correction explains what changed, not just the final answer.

01 / Standard#Your turn

a=9,\quad b=2

a,b>0 and e>1; a distance difference is absolute, and an asymptote is not part of the curve.

Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1

Translate the geometric condition into a coordinate equation.

Hint 2

Use this intermediate relation.

e=c/a

Worked solution

The requested value is 1.02439382859.

Checks and common pitfalls: The computed value must exceed one.

Think first. Reveal a hint when the class is ready.

Teacher preparation and assessment

Parameters: For x²/a²−y²/b²=1, c²=a²+b² and asymptotes are y=±(b/a)x.
Branch conditions: a,b>0 and e>1; a distance difference is absolute, and an asymptote is not part of the curve.