Final answer:
To calculate the length of the triangular border on the front of the roof, add the lengths of all three sides: 2.1 feet + 2.1 feet + 4 feet, which equals 8.2 feet. Thus, the correct answer is 8.2 feet (option C) for the length of the border.
Step-by-step explanation:
The length of the triangular border on the front of the roof for a custom-built doghouse is determined by adding the lengths of its sides.
The roof is described as a triangle with two equal sides (isosceles triangle) with side lengths of 2.1 feet each, and a base of 4 feet.
To find the total length of the triangular border, we simply add up the lengths of all three sides:
- Side 1: 2.1 feet
- Side 2: 2.1 feet
- Base: 4 feet
Add these together: 2.1 + 2.1 + 4 = 8.2 feet. So, the length of the triangular border is 8.2 feet.
Therefore, the answer is C. 8.2 feet.