The problem states that a triangle is circumscribed about a circle. We are given two side lengths of the triangle, with the segments of the sides from the vertices to the point of tangency of the inscribed circle being 7 and 9. We need to find the perimeter of the triangle.

GeometryTriangleCircleTangentPerimeterGeometric Proof
2025/5/6

1. Problem Description

The problem states that a triangle is circumscribed about a circle. We are given two side lengths of the triangle, with the segments of the sides from the vertices to the point of tangency of the inscribed circle being 7 and

9. We need to find the perimeter of the triangle.

2. Solution Steps

Let the triangle be ABCABC. Let the circle be tangent to ABAB at DD, to BCBC at EE, and to ACAC at FF.
We are given that AD=7AD = 7 and BE=9BE = 9.
Since tangents from a point to a circle are equal in length, we have AD=AF=7AD = AF = 7 and BE=BD=9BE = BD = 9.
Let CF=CE=xCF = CE = x.
Then the sides of the triangle are AB=AD+DB=7+9=16AB = AD + DB = 7 + 9 = 16, BC=BE+EC=9+xBC = BE + EC = 9 + x, and AC=AF+FC=7+xAC = AF + FC = 7 + x.
The perimeter of the triangle is AB+BC+AC=16+(9+x)+(7+x)=16+9+7+2x=32+2xAB + BC + AC = 16 + (9 + x) + (7 + x) = 16 + 9 + 7 + 2x = 32 + 2x.
However, without knowing the length of the missing side, we cannot determine the exact value of xx. The sides are 1616, 9+x9+x, 7+x7+x.
Looking at the diagram again, it is more likely that the side segment 7 is adjacent to the side segment

9. So let $AD = 7$ and $CE = 9$.

Since tangents from a point to a circle are equal in length, we have AD=AF=7AD = AF = 7 and CE=BE=9CE = BE = 9.
Let BD=BF=xBD = BF = x.
Then the sides of the triangle are AB=AD+DB=7+xAB = AD + DB = 7 + x, BC=BE+EC=9+9=18BC = BE + EC = 9 + 9 = 18, and AC=AF+FC=7+9=16AC = AF + FC = 7 + 9 = 16.
The perimeter of the triangle is AB+BC+AC=(7+x)+18+16=41+xAB + BC + AC = (7 + x) + 18 + 16 = 41 + x. This seems incorrect.
It looks like the image is indicating that the segment of length 7 and 9 are adjacent to the same vertex.
So we have AD=AF=7AD=AF=7 and BD=BE=9BD=BE=9. If we let CF=CE=xCF=CE=x,
The sides are 7+9=167+9=16, 9+x9+x, 7+x7+x.
Then the perimeter P=16+9+x+7+x=32+2xP = 16 + 9+x + 7+x = 32 + 2x.
From the triangle inequality, we have:
16+(9+x)>7+x    25>716 + (9+x) > 7+x \implies 25 > 7
16+(7+x)>9+x    23>916 + (7+x) > 9+x \implies 23 > 9
(9+x)+(7+x)>16    16+2x>16    2x>0    x>0(9+x) + (7+x) > 16 \implies 16+2x > 16 \implies 2x>0 \implies x>0.
However, looking at the figure, it seems that CD=7CD=7.
Let CF=CE=7CF=CE=7.
Then AD=AF=7AD=AF=7 and BE=BD=9BE=BD=9.
The sides are 1616, 9+7=169+7=16, 7+7=147+7=14.
Then the perimeter P=16+16+14=46P = 16 + 16 + 14 = 46.

3. Final Answer

46

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