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HomeJEE MainMathematicsInverse Trigonometric Functions › cos⁻¹(cos(5π/4)) =

cos⁻¹(cos(5π/4)) =

Aπ/4
B3π/4 (since cos(5π/4) = -√2/2 = cos(3π/4))
C-π/4
D5π/4
Answer & Solution
Correct answer: B. 3π/4 (since cos(5π/4) = -√2/2 = cos(3π/4))
cos(5π/4) = -√2/2. arccos(-√2/2) = 3π/4 (principal range [0, π]). Note: NOT 5π/4.
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