## 11 Feb Indian National Mathematical Olympiad 2012

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The Indian National Mathematical Olympiad 2012 was held on 5th February, 2012 at various centres all over the country. The North East had three centres at Guwahati, Shillong and Agartala. The questions are given below:

1. Let $$ABCD$$ be a quadrilateral inscribed in a circle. Suppose $$AB=sqrt{2+sqrt{2}}$$ and $$AB$$ subtends $$135$$ degrees at center of circle . Find the maximum possible area of $$ABCD$$.

2. Let $$p_1<p_2<p_3<p_4$$ and $$q_1<q_2<q_3<q_4$$ be two sets of prime numbers, such that $$p_4$$ – $$p_1 = 8$$ and $$q_4$$ – $$q_1= 8$$. Suppose $$p_1 > 5$$ and $$q_1>5$$. Prove that $$30$$ divides $$p_1$$ – $$q_1$$.

3. Define a sequence $$langle f_n (x)rangle_{ninmathbb N_0}$$ of functions as

$$f_0(x)=1, f_1(x)=x, (f_n(x))^2-1=f_{n-1}(x)f_{n+1}(x), text{for} ngeq 1.$$

Prove that each $$f_n(x)$$ is a polynomial with integer coefficients.

4. Let $$ABC$$ be a triangle. An interior point $$P$$ of $$ABC$$ is said to be good if we can find exactly $$27$$ rays emanating from $$P$$ intersecting the sides of the triangle $$ABC$$ such that the triangle is divided by these rays into $$27$$ smaller triangles of equal area. Determine the number of good points for a given triangle $$ABC$$.

5. Let $$ABC$$ be an acute angled triangle. Let $$D,E,F$$ be points on $$BC, CA, AB$$ such that $$AD$$ is the median, $$BE$$ is the internal bisector and $$CF$$ is the altitude. Suppose that $$angle FDE=angle C, angle DEF=angle A$$ and $$angle EFD=angle B.$$ Show that $$ABC$$ is equilateral.

6. Let $$f : mathbb{Z} to mathbb{Z}$$ be a function satisfying $$f(0) ne 0$$, $$f(1) = 0$$ and

$$(i) f(xy) + f(x)f(y) = f(x) + f(y)$$

$$(ii)left(f(x-y)$$ – $$f(0)right ) f(x)f(y) = 0 $$

for all $$x,y in mathbb{Z}$$, simultaneously.

$$(a)$$ Find the set of all possible values of the function $$f$$.

$$(b)$$ If $$f(10) ne 0$$ and $$f(2) = 0$$, find the set of all integers $$n$$ such that $$f(n) ne 0$$.

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Managing Editor of the English Section, Gonit Sora and Research Fellow, Faculty of Mathematics, University of Vienna.

## priyam ladha

Posted at 23:41h, 21 Aprilwhen is next maths Olympiad is going to held in session 2012 to 2013 for class 11th please give me information by calling on 8107971000.

thanking you!!!

## Gonit Sora

Posted at 13:33h, 24 AprilThe next Olympiad will be the RMO in the first Sunday of November 2012.

## oindrila das

Posted at 20:16h, 09 Septemberwhen is the next maths olympiad for the students of class11 this year

## Gonit Sora

Posted at 21:42h, 10 SeptemberRMO in December 2012.