The triangle shown below has side lengths 37, 38 and 39 inches. Which of the following expression gives the measure of the largest angle of the triangle?
(Note : For every triangle with sides of length a, b and c that are opposite `/_A, /_B, and /_C`, respectively. `c^(2) = a^(2) + b^(2) - 2ab cos C`.)

Options

A. `cos^(-1)(-(37^(2) - 38^(2) - 39^(2))/(2(38)(39)))`
B. `cos^(-1)(-(39^(2) - 37^(2) -38^(2))/(2(37)(38)))`
C. `cos^(-1)(37^(2) - 38^(2) - 39^(2) + 2(38)(39))`
D. `cos^(-1)(38^(2) - 37^(2) - 39^(2) + 2(37)(39))`

Answer

B