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Unformatted text preview: STEP I, 1999 2 Section A: Pure Mathematics 1 How many integers greater than or equal to zero and less than a million are not divisible by 2 or 5? What is the average value of these integers? How many integers greater than or equal to zero and less than 4179 are not divisible by 3 or 7? What is the average value of these integers? 2 A point moves in the x y plane so that the sum of the squares of its distances from the three fixed points ( x 1 , y 1 ), ( x 2 , y 2 ), and ( x 3 , y 3 ) is always a 2 . Find the equation of the locus of the point and interpret it geometrically. Explain why a 2 cannot be less than the sum of the squares of the distances of the three points from their centroid. [The centroid has coordinates ( x, y ) where 3 x = x 1 + x 2 + x 3 , 3 y = y 1 + y 2 + y 3 . ] 3 The n positive numbers x 1 , x 2 , . . . , x n , where n > 3, satisfy x 1 = 1 + 1 x 2 , x 2 = 1 + 1 x 3 , . . . , x n 1 = 1 + 1 x n , and also x n = 1 + 1 x 1 . Show that (i) x 1 , x 2 , . . . , x n > 1, (ii) x 1 x 2 = x 2 x 3 x 2 x 3 , (iii) x 1 = x 2 = = x n . Hence find the value of x 1 . 4 Sketch the following subsets of the x y plane: (i)  x  +  y  6 1 ; (ii)  x 1  +  y 1  6 1 ; (iii)  x 1    y + 1  6 1 ; (iv)  x  y 2  6 1 . STEP I, 1999 3 5 For this question, you may use the following approximations, valid if is small: sin and cos 1 2 / 2 . A satellite X is directly above the point Y on the Earths surface and can just be seen (on the horizon) from another point Z on the Earths surface. The radius of the Earth is R and the height of the satellite above the Earth is...
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This note was uploaded on 04/01/2012 for the course MATH 1016 taught by Professor Rotar during the Spring '12 term at Central Lancashire.
 Spring '12
 rotar
 Math, Integers

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