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Triangle ABC  has altitudes  AD, BE, and CF. and  If  AD= 12, BE=16, and CF is a positive integer, then find the largest possible value of CF.

 Aug 13, 2024
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To find the largest possible value of CF, we'll use the relationship between the altitudes in a triangle and its area. The area Δ of a triangle can be expressed using any of its altitudes:

 

Δ=12×base×height

 

For triangle ABC, we have the following relationships:

 

- Δ=12×BC×AD=12×CA×BE=12×AB×CF

 

Let the side lengths be a=BC, b=CA, and c=AB. Then:

 

Δ=12×a×12=12×b×16=12×c×CF

 

This simplifies to:

 

Δ=6a=8b=12c×CF

 

Equating these expressions:

 

6a=8band6a=12c×CF

 

### Step 1: Solve for a and b


From 6a=8b:

 

ab=86=43

 

Thus, a=43b.

 

 

### Step 2: Substitute into 6a=12c×CF


Substitute a=43b into 6a=12c×CF:

 

6×43b=12c×CF

 

Simplifying:

 

8b=12c×CFso16b=c×CF

 

### Step 3: Find the Maximum Value of CF


We need to maximize CF, which is a positive integer. Since 16b=c×CF, and c and CF are integers, CF is maximized when c is minimized.

 

Given the relationship 6a=8b, a=43b, and c=16bCF, the smallest integer value of c occurs when CF is as large as possible.

 

If CF=16, then:

 

16b=c×16soc=b

 

Since c is minimized and CF is maximized at 16, this is the largest possible value for CF.

 

Thus, the largest possible value of CF is 24.

 Aug 14, 2024

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