Difference between revisions of "2007 AIME II Problems/Problem 3"
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== Problem == | == Problem == | ||
[[Square]] <math>ABCD</math> has side length <math>13</math>, and [[point]]s <math>E</math> and <math>F</math> are exterior to the square such that <math>BE=DF=5</math> and <math>AE=CF=12</math>. Find <math>EF^{2}</math>. | [[Square]] <math>ABCD</math> has side length <math>13</math>, and [[point]]s <math>E</math> and <math>F</math> are exterior to the square such that <math>BE=DF=5</math> and <math>AE=CF=12</math>. Find <math>EF^{2}</math>. | ||
+ | <asy>unitsize(0.2 cm); | ||
− | + | pair A, B, C, D, E, F; | |
+ | |||
+ | A = (0,13); | ||
+ | B = (13,13); | ||
+ | C = (13,0); | ||
+ | D = (0,0); | ||
+ | E = A + (12*12/13,5*12/13); | ||
+ | F = D + (5*5/13,-5*12/13); | ||
+ | |||
+ | draw(A--B--C--D--cycle); | ||
+ | draw(A--E--B); | ||
+ | draw(C--F--D); | ||
+ | |||
+ | dot("$A$", A, W); | ||
+ | dot("$B$", B, dir(0)); | ||
+ | dot("$C$", C, dir(0)); | ||
+ | dot("$D$", D, W); | ||
+ | dot("$E$", E, N); | ||
+ | dot("$F$", F, S);</asy> | ||
__TOC__ | __TOC__ | ||
+ | |||
== Solution == | == Solution == | ||
Revision as of 15:48, 1 May 2015
Problem
Square has side length , and points and are exterior to the square such that and . Find .
Solution
Solution 1
Extend and to their points of intersection. Since and are both right triangles, we can come to the conclusion that the two new triangles are also congruent to these two (use ASA, as we know all the sides are and the angles are mostly complementary). Thus, we create a square with sides .
is the diagonal of the square, with length ; the answer is .
Solution 2
A slightly more analytic/brute-force approach:
Drop perpendiculars from and to and , respectively; construct right triangle with right angle at K and . Since , we have . Similarly, . Since , we have .
Now, we see that . Also, . By the Pythagorean Theorem, we have . Therefore, .
See also
2007 AIME II (Problems • Answer Key • Resources) | ||
Preceded by Problem 2 |
Followed by Problem 4 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 | ||
All AIME Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.