If sin⁻¹x = π/5 for some x in [−1,1], then cos⁻¹x equals:

If sin⁻¹x = π/5 for some x in [−1,1], then cos⁻¹x equals:

• A. π/5
• B. 2π/5
• C. 3π/10
• D. π/10

Answer: C) 3π/10

Explanation: sin⁻¹x + cos⁻¹x = π/2. So cos⁻¹x = π/2 − π/5 = (5π−2π)/10 = 3π/10.