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geometry intermediate
Problem
Find the area of a triangle with side lengths 13, 17, and .
Solution
We begin by drawing a diagram and labeling the vertices , , and as shown:
We drop a perpendicular from to and label the intersection point . divides into two segments and that sum to 17, so let and . Let the height of the triangle, , have length .
Now we have two right triangles, so we can use the Pythagorean theorem on both triangles to write two equations in terms of and . From , we have and from , we have Expanding the second equation gives ; substituting the first equation into the second gives Simplifying and solving for yields , so . Plugging this value into the first equation gives so . Finally, we can compute the area of to be
We drop a perpendicular from to and label the intersection point . divides into two segments and that sum to 17, so let and . Let the height of the triangle, , have length .
Now we have two right triangles, so we can use the Pythagorean theorem on both triangles to write two equations in terms of and . From , we have and from , we have Expanding the second equation gives ; substituting the first equation into the second gives Simplifying and solving for yields , so . Plugging this value into the first equation gives so . Finally, we can compute the area of to be
Final answer
102