A) 0
B) 1
C) 5
D) 10
Correct Answer: B
Solution :
\[\because \] \[\sum\limits_{r=1}^{5}{\cos rx=5}\] \[\Rightarrow \]\[cos\text{ }x+cos\text{ }2x+cos\text{ }3x+cos\text{ }4x+cos\text{ }5x=5\]which is possible only, when \[cos\text{ }x=cos\text{ }2x=cos\text{ }3x=cos\text{ }4x=cos\text{ }5x=1\]and is satisfied by\[x=0\]only. Hence, the number of solution = 1You need to login to perform this action.
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