Thursday, 3 October 2019

summation - The value of $sum _{n=1}^{infty }{left(qright)^nleft(sin(na)right), |q|

I need to solve this sum, but unfortunately I have no idea how to start.I would be grateful for every advice.




$$\sum _{n=1}^{\infty }{\left(q\right)^n\left(\sin(na)\right), |q|<1}$$


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