Sunday, 9 February 2014

sequences and series - trigonometric summation with arithmetic progression of angles and coefficients

How can we sum up sin and cos series when the angles and also coefficients are in arithmetic progression?
Such as cos(x)+2cos(2x)+3cos(3x)+.......+ncos(nx)

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real analysis - How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$

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