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imc

geometry intermediate

Problem

What is the perimeter of the boundary of the region consisting of all points which can be expressed as with , and ?
(A)
(B)
(C)
(D)
(E)
Solution
Notice that we are given a parametric form of the region, and is used in both and . We first fix and to , and graph from . When is , we have the point , and when is , we have the point . We see that since this is a directly proportional function, we can just connect the dots like this: Now, when we vary from to , this line is translated to the right units: We know that any points in the region between the line (or rather segment) and its translation satisfy and , so we shade in the region: We can also shift this quadrilateral one unit up, because of . Thus, this is our figure: The length of the boundary is simply ( can be obtained by Pythagorean theorem since we have side lengths and .). This equals
Final answer
E