2005 AIME I Problems/Problem 7
Problem
In quadrilateral and Given that where and are positive integers, find
Contents
Solution
Solution 1
Draw line segment such that line is concurrent with line . Then, is an isosceles trapezoid so , and and . We are given that . Since , using Law of Cosines on gives which gives . Adding to both sides gives , so . and are both , so and . , and therefore .
Solution 2
Draw the perpendiculars from and to , labeling the intersection points as and . This forms 2 right triangles, so and . Also, if we draw the horizontal line extending from to a point on the line , we find another right triangle . . The Pythagorean Theorem yields that , so . Therefore, , and .
Solution 3
Extend and to an intersection at point . We get an equilateral triangle . We denote the length of a side of as and solve for it using the Law of Cosines: This simplifies to ; the quadratic formula yields the (discard the negative result) same result of .
Solution 4
Extend and to meet at point , forming an equilateral triangle . Draw a line from parallel to so that it intersects at point . Then, apply Stewart's Theorem on . Let . By the quadratic formula (discarding the negative result), , giving for a final answer of .
See also
2005 AIME I (Problems • Answer Key • Resources) | ||
Preceded by Problem 6 |
Followed by Problem 8 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 | ||
All AIME Problems and Solutions |
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