We have:
Applying cosines law we have:
5 ^ 2 = 7 ^ 2 + 6 ^ 2 - 2 * 7 * 6 * cos (F)
Clearing the angle we have:
cos (F) = (5 ^ 2 - 7 ^ 2 - 6 ^ 2) / (- 2 * 7 * 6)
cos (F) = 0.714285714
Then, clearing the angle:
F = acos (0.714285714)
F = 44.42 degrees
Rounding:
F = 44 degrees
Answer:
F = 44 degrees
option 1