The value of cos⁻¹(4/5) + cos⁻¹(12/13) is:
The value of cos⁻¹(4/5) + cos⁻¹(12/13) is:
- A. cos⁻¹(16/65)
- B. cos⁻¹(33/65)
- C. cos⁻¹(63/65)
- D. cos⁻¹(48/65)
Answer: B) cos⁻¹(33/65)
Explanation: Let A = cos⁻¹(4/5) and B = cos⁻¹(12/13). cos(A+B) = cosA cosB − sinA sinB = (4/5)(12/13) − (3/5)(5/13) = 48/65 − 15/65 = 33/65.
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