The range of the function,
$$f(x) = {\log _{\sqrt 5 }}\left( {3 + \cos \left( {{{3\pi } \over 4} + x} \right) + \cos \left( {{\pi \over 4} + x} \right) + \cos \left( {{\pi \over 4} - x} \right) - \cos \left( {{{3\pi } \over 4} - x} \right)} \right)$$ is :
$$f(x) = {\log _{\sqrt 5 }}\left( {3 + \cos \left( {{{3\pi } \over 4} + x} \right) + \cos \left( {{\pi \over 4} + x} \right) + \cos \left( {{\pi \over 4} - x} \right) - \cos \left( {{{3\pi } \over 4} - x} \right)} \right)$$ is :
- A$$\left( {0,\sqrt 5 } \right)$$
- B[$$-$$2, 2]
- C$$\left[ {{1 \over {\sqrt 5 }},\sqrt 5 } \right]$$
- D[0, 2]
✓ Correct answer: D
Want the full step-by-step reasoning?