Difference between revisions of "1993 IMO Problems"
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− | ==Problem 1== | + | Problems of the 1993 [[IMO]]. |
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+ | ==Day I== | ||
+ | ===Problem 1=== | ||
Let <math>f(x)=x^n+5x^{n-1}+3</math>, where <math>n>1</math> is an integer. Prove that <math>f(x)</math> cannot be expressed as the product of two nonconstant polynomials with integer coefficients. | Let <math>f(x)=x^n+5x^{n-1}+3</math>, where <math>n>1</math> is an integer. Prove that <math>f(x)</math> cannot be expressed as the product of two nonconstant polynomials with integer coefficients. | ||
− | ==Problem 2== | + | [[1993 IMO Problems/Problem 1|Solution]] |
+ | |||
+ | ===Problem 2=== | ||
Let <math>D</math> be a point inside acute triangle <math>ABC</math> such that <math>\angle ADB=\angle ACB+\pi/2</math> and <math>AC\cdot BD=AD\cdot BC</math>. | Let <math>D</math> be a point inside acute triangle <math>ABC</math> such that <math>\angle ADB=\angle ACB+\pi/2</math> and <math>AC\cdot BD=AD\cdot BC</math>. | ||
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(b) Prove that the tangents at <math>C</math> to the circumcircles of <math>\triangle ACD</math> and <math>\triangle BCD</math> are perpendicular. | (b) Prove that the tangents at <math>C</math> to the circumcircles of <math>\triangle ACD</math> and <math>\triangle BCD</math> are perpendicular. | ||
− | ==Problem 3== | + | [[1993 IMO Problems/Problem 2|Solution]] |
+ | |||
+ | ===Problem 3=== | ||
On an infinite chessboard, a game is played as follows. At the start, <math>n^2</math> pieces are arranged on the chessboard in an <math>n</math> by <math>n</math> block of adjoining squares, one piece in each square. A move in the game is a jump in a horizontal or vertical direction over an adjacent occupied square to an unoccupied square immediately beyond. The piece which has been jumped over is removed. Find those values of <math>n</math> for which the game can end with only one piece remaining on the board. | On an infinite chessboard, a game is played as follows. At the start, <math>n^2</math> pieces are arranged on the chessboard in an <math>n</math> by <math>n</math> block of adjoining squares, one piece in each square. A move in the game is a jump in a horizontal or vertical direction over an adjacent occupied square to an unoccupied square immediately beyond. The piece which has been jumped over is removed. Find those values of <math>n</math> for which the game can end with only one piece remaining on the board. | ||
− | ==Problem 4== | + | [[1993 IMO Problems/Problem 3|Solution]] |
+ | |||
+ | ==Day II== | ||
+ | ===Problem 4=== | ||
For three points <math>P,Q,R</math> in the plane, we define <math>m(PQR)</math> as the minimum length of the three altitudes of <math>\triangle PQR</math>. (If the points are collinear, we set <math>m(PQR)=0</math>.) | For three points <math>P,Q,R</math> in the plane, we define <math>m(PQR)</math> as the minimum length of the three altitudes of <math>\triangle PQR</math>. (If the points are collinear, we set <math>m(PQR)=0</math>.) | ||
Prove that for points <math>A,B,C,X</math> in the plane, <cmath>m(ABC)\le m(ABX)+m(AXC)+m(XBC).</cmath> | Prove that for points <math>A,B,C,X</math> in the plane, <cmath>m(ABC)\le m(ABX)+m(AXC)+m(XBC).</cmath> | ||
− | ==Problem 5== | + | [[1993 IMO Problems/Problem 4|Solution]] |
+ | |||
+ | ===Problem 5=== | ||
Does there exist a function <math>f:\textbf{N}\rightarrow\textbf{N}</math> such that <math>f(1)=2,f(f(n))=f(n)+n</math> for all <math>n\in\textbf{N}</math> and <math>f(n)<f(n+1)</math> for all <math>n\in\textbf{N}</math>? | Does there exist a function <math>f:\textbf{N}\rightarrow\textbf{N}</math> such that <math>f(1)=2,f(f(n))=f(n)+n</math> for all <math>n\in\textbf{N}</math> and <math>f(n)<f(n+1)</math> for all <math>n\in\textbf{N}</math>? | ||
− | ==Problem 6== | + | [[1993 IMO Problems/Problem 5|Solution]] |
+ | |||
+ | ===Problem 6=== | ||
There are <math>n</math> lamps <math>L_0, \ldots , L_{n-1}</math> in a circle (<math>n > 1</math>), where we denote <math>L_{n+k} = L_k</math>. (A lamp at all times is either on or off.) Perform steps <math>s_0, s_1, \ldots</math> as follows: at step <math>s_i</math>, if <math>L_{i-1}</math> is lit, switch <math>L_i</math> from on to off or vice versa, otherwise do nothing. Initially all lamps are on. Show that: | There are <math>n</math> lamps <math>L_0, \ldots , L_{n-1}</math> in a circle (<math>n > 1</math>), where we denote <math>L_{n+k} = L_k</math>. (A lamp at all times is either on or off.) Perform steps <math>s_0, s_1, \ldots</math> as follows: at step <math>s_i</math>, if <math>L_{i-1}</math> is lit, switch <math>L_i</math> from on to off or vice versa, otherwise do nothing. Initially all lamps are on. Show that: | ||
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(c) If <math>n = 2^k + 1</math>, we can take <math>M(n) = n^2 - n + 1.</math> | (c) If <math>n = 2^k + 1</math>, we can take <math>M(n) = n^2 - n + 1.</math> | ||
+ | |||
+ | [[1993 IMO Problems/Problem 6|Solution]] | ||
+ | |||
+ | ==See Also== | ||
+ | {{IMO box|year=1993|before=[[1992 IMO]]|after=[[1994 IMO]]}} |
Latest revision as of 20:34, 4 July 2024
Problems of the 1993 IMO.
Contents
Day I
Problem 1
Let , where is an integer. Prove that cannot be expressed as the product of two nonconstant polynomials with integer coefficients.
Problem 2
Let be a point inside acute triangle such that and .
(a) Compute the ratio
(b) Prove that the tangents at to the circumcircles of and are perpendicular.
Problem 3
On an infinite chessboard, a game is played as follows. At the start, pieces are arranged on the chessboard in an by block of adjoining squares, one piece in each square. A move in the game is a jump in a horizontal or vertical direction over an adjacent occupied square to an unoccupied square immediately beyond. The piece which has been jumped over is removed. Find those values of for which the game can end with only one piece remaining on the board.
Day II
Problem 4
For three points in the plane, we define as the minimum length of the three altitudes of . (If the points are collinear, we set .)
Prove that for points in the plane,
Problem 5
Does there exist a function such that for all and for all ?
Problem 6
There are lamps in a circle (), where we denote . (A lamp at all times is either on or off.) Perform steps as follows: at step , if is lit, switch from on to off or vice versa, otherwise do nothing. Initially all lamps are on. Show that:
(a) There is a positive integer such that after steps all the lamps are on again;
(b) If , we can take ;
(c) If , we can take
See Also
1993 IMO (Problems) • Resources | ||
Preceded by 1992 IMO |
1 • 2 • 3 • 4 • 5 • 6 | Followed by 1994 IMO |
All IMO Problems and Solutions |