The number of solutions of $5^{1+|\sin x|+|\sin x|^2+\cdots}=25$ for $x\in(-\pi,\pi)$ is
- A. 2
- B. 0
- C. 4
- D. Infinite
✅ Correct Answer: 4
Explanation
The series is a geometric series $1+|\sin x|+|\sin x|^2+\cdots = 1/(1-|\sin x|)$ Given $5^{1/(1-|\sin x|)}=5^2$ So $1/(1-|\sin x|)=2$ $|\sin x|=1/2$ For $x\in(-\pi,\pi)$, there are $4$ solutions
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