Final answer:
The value of ab cos(c) is c² - a² - b².
Step-by-step explanation:
The law of cosines, a² + b² - 2ab cos(c) = c², can be rearranged to solve for ab cos(c).
To find ab cos(c), we can subtract a² and b² from both sides of the equation:
ab cos(c) = c² - a² - b²
Therefore, the value of ab cos(c) is c² - a² - b².