KCET · Maths · Vector Algebra

The area of the triangle formed by the lines joining the vertex of the parabola \( x^{2}=12 y \) to the
ends of Latus rectum is

A \( 18 \mathrm{sq} \). units
B \( 19 \mathrm{sq} \). units
C \( 20 \mathrm{sq} . \) units
D \( 17 \mathrm{sq} . \) units

Verified Solution

Answer & Solution

Correct Answer

(A) \( 18 \mathrm{sq} \). units

Step-by-step Solution

Detailed explanation

Given that, \(\chi^{2}=12 y \rightarrow(1)\)
General equation of parabola is \(\chi^{2}=4 a y\)
So, \(4 a=12 \Rightarrow a=3\)
So, area of triangle is
\(\frac{1}{2} \times\) base \(\times\) height
\(\frac{1}{4}(4|a|)(|a|)=\frac{1}{2}(12)(3)\)
\(=6 \times 3=18\) sq. units

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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The area of the triangle formed by the lines joining the vertex of the parabola \( x^{2}=12 y \) to theends of Latus rectum is

Step-by-step Solution

The area of the triangle formed by the lines joining the vertex of the parabola \( x^{2}=12 y \) to the
ends of Latus rectum is