Question bank/JEE Main/Mathematics

JEE MainMathematicsToughStraight Lines

Let H be the orthocenter of ΔABC\mathrm{\Delta}ABC where
A≡(0,0),B≡(8,0)A \equiv (0,0),B \equiv (8,0) and C≡(4,43)C \equiv (4,4\sqrt{3}). If
G1,G2,G3,……… G_{1},G_{2},G_{3},\ldots\ldots\ldots\ are centroids of
ΔAHB,  ΔAG1B,  ΔAG2B,…………\mathrm{\Delta}AHB,\ \ \mathrm{\Delta}AG_{1}B,\ \ \Delta AG_{2}B,\ldots\ldots\ldots\ldots
respectively then find value of

Limn→∞∑i=1n\mspace2mu ArΔAGiB{Lim}_{n \rightarrow \infty}{\sum_{i = 1}^{n}\mspace{2mu}\ Ar}\mathrm{\Delta}AG_{i}B

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ΔABC\mathrm{\Delta}ABC dk yEcdsUnz gS] tgk¡
ΔAHB,  ΔAG1B,  ΔAG2B,…………\mathrm{\Delta}AHB,\ \ \mathrm{\Delta}AG_{1}B,\ \ \Delta AG_{2}B,\ldots\ldots\ldots\ldots
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Limn→∞∑i=1n\mspace2mu ArΔAGiB{Lim}_{n \rightarrow \infty}{\sum_{i = 1}^{n}\mspace{2mu}\ Ar}\mathrm{\Delta}AG_{i}B
dk eku Kkr dhft, &

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Ar(ΔAGiB)Ar(\Delta AG_{i}B) f=Hkqt ΔAGiB\Delta AG_{i}B

Show answer and solution
ΔABC\mathrm{\Delta}ABC is equilateral ⇒\Rightarrow H is centroid
of

△ABC⇒ar(ΔAHB)=13ar(ΔABC)=163\bigtriangleup ABC \Rightarrow ar(\Delta AHB) = \frac{1}{3}ar(\Delta ABC) = \frac{16}{\sqrt{3}}
Now
G1G_{1} is centroid of
ΔABC⇒ar(ΔAG1B)=13 ar(ΔAHB)=13(163)\Delta ABC \Rightarrow ar\left( \Delta AG_{1}B \right) = \frac{1}{3}\ ar(\Delta AHB) = \frac{1}{3}\left( \frac{16}{\sqrt{3}} \right)

Source: Grass-G / M-25 Mathematics Paper 7 Jan.docx

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