Answer: B. between 7 and 10 ft
Explanation: To determine the possible length of \( AB \) in \( \triangle ABC \), we use the triangle inequality theorem. This theorem states that the sum of the lengths of any two sides of a triangle must be greater than the length of the third side. Additionally, the Law of Cosines can be used to find the exact length of \( AB \).
Steps:
- Triangle Inequality Theorem:
- For side \( AB \):
- \( AB + BC > AC \) implies \( AB + 7 > 10 \) → \( AB > 3 \)
- \( AB + AC > BC \) implies \( AB + 10 > 7 \) → \( AB > -3 \) (not useful since AB is positive)
- \( AC + BC > AB \) implies \( 10 + 7 > AB \) → \( AB < 17 \)
Therefore, by the triangle inequality, \( AB \) must be between 3 and 17 ft.
- Law of Cosines:
- Using the Law of Cosines to find the exact length of \( AB \):
Since \( AB \approx 7.32 \), it falls between 7 and 10 ft, confirming option B.