49 Test file number 84

  49.1 Problem number 50
  49.2 Problem number 51
  49.3 Problem number 52
  49.4 Problem number 53
  49.5 Problem number 54
  49.6 Problem number 55

Test folder name:

test_cases/4_Trig_functions/4.2_Cosine/84_4.2.1.1-a+b_cos-^n