Find the sum $1+\cos (x)+\cos (2x)+\cos (3x)+....+\cos (n-1)x$
9479
$\sum \cos$ when angles are in arithmetic progression
65698
Proving $\sum\limits_{k=0}^{n}\cos(kx)=\frac{1}{2}+\frac{\sin(\frac{2n+1}{2}x)}{2\sin(x/2)}$
138172
Find the sum to n terms of the series $\frac{1}{1.2.3}+\frac{3}{2.3.4}+\frac{5}{3.4.5}+\frac{7}{4.5.6}+\cdots$..
64581
How to find the sum $\sum\limits_{k=1}^n (k^2+k+1)k!$?
89561
Find the sum of angles without trigonometry?
114414
Sum of $\sum_{k=1}^n\sin{k\theta}$
153409
Sum of $1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\frac{1}{6}+\frac{1}{8}+\frac{1}{9}+\frac{1}{12}+\cdots$
74120
Find the value of $\sum_{n=1}^{\infty} \frac{2}{n}-\frac{4}{2n+1}$
141978
How to find the infinite sum
113189
Find the sum of the series $1^2-2^2+3^2-4^2+...-(2n)^2$
136066
Find the sum $\sum _{n=1}^{\infty }\left(\sqrt{n+2}-2\sqrt{n+1}+\sqrt{n}\right)$
9610
Find the sum of $\sum\limits_{n=1}^{\infty} \frac{x^{n}}{n(n+1)}$
152588
Expression for $n+n(n-1)+n(n-1)(n-2)+...+n!$
143753
Please help me to find the sum $\sum\limits_{n\geq1} \frac{\sin(nx)}{n^2}$
30851
Find the summation $\frac{1}{1!}+\frac{1+2}{2!}+\frac{1+2+3}{3!}+ \cdots$
142610
Solving $\sin x\cos3x+\cos x\sin3x=\sqrt{3}/2$ in the interval $[0,2\pi]$
89319
How can I find all the solutions of $\sin^5x+\cos^3x=1$