Answer: 1) The approximate value of x is 15°,
2) The approximate value of cosine of the angle that is complementary to x is 0.2588.
Explanation:
1) According to the question,



2) Now, the complementary of x = 90° - x = 90° - 15° = 75°
Hence, the cosine of the angle that is complementary to x is,
cos (75°) = 0.2588190451 ≈ 0.2588
Note : The two angles are complementary angles if their sum is 90°.