NTA Abhyas 2020
- Exam
- NTA Abhyas
- Year
- 2020
- Subject
- Mathematics
- Chapter
- Ellipse
NTA Abhyas 2020 · Mathematics · Ellipse
The point on the ellipse x^ 2 6 + y^ 2 3 = 1 which is nearest to...
The point on the ellipse which is nearest to the line is
Options
- A
- B
- C
- D
Correct answer
D.
Step-by-step solution
Shortest distance always lies along the common normal
Slope of common normal is
Now, the equation of the normal at the point \left(acos \theta, bsin \theta\right)on\dfrac{x2}{a2} + \dfrac{y2}{b2} = 1\dfrac{ax}{cos\theta} - \dfrac{by}{sin\theta} = a^{2} - b^{2},\dfrac{a}{b}tan \theta⇒ \dfrac{\sqrt{6}}{\sqrt{3}}tan \theta = 1 ⇒ tan \theta = \dfrac{1}{\sqrt{2}}⇒ sin \theta = \dfrac{1}{\sqrt{3}}cos \theta = \dfrac{\sqrt{2}}{\sqrt{3}}sin \theta = - \dfrac{1}{3}, cos \theta = - \dfrac{2}{3}⇒Nearest point is \left(\sqrt{6}\left(\dfrac{\sqrt{2}}{\sqrt{3}}\right), \sqrt{3}\left(\dfrac{1}{\sqrt{3}}\right)\right) = \left(2,1\right)
Slope of common normal is
Now, the equation of the normal at the point \left(acos \theta, bsin \theta\right)on\dfrac{x2}{a2} + \dfrac{y2}{b2} = 1\dfrac{ax}{cos\theta} - \dfrac{by}{sin\theta} = a^{2} - b^{2},\dfrac{a}{b}tan \theta⇒ \dfrac{\sqrt{6}}{\sqrt{3}}tan \theta = 1 ⇒ tan \theta = \dfrac{1}{\sqrt{2}}⇒ sin \theta = \dfrac{1}{\sqrt{3}}cos \theta = \dfrac{\sqrt{2}}{\sqrt{3}}sin \theta = - \dfrac{1}{3}, cos \theta = - \dfrac{2}{3}⇒Nearest point is \left(\sqrt{6}\left(\dfrac{\sqrt{2}}{\sqrt{3}}\right), \sqrt{3}\left(\dfrac{1}{\sqrt{3}}\right)\right) = \left(2,1\right)