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.
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.