This is a modified summation question taken from HCI. I think it forces the students to think out of the box, and we all know how scary trigonometry and summation is together.
Given ![\sum_{r=1}^{n}cos[(2r-1){\theta}] = \frac{sin(2n\theta)}{2sin\theta}](http://theculture.sg/wp-content/ql-cache/quicklatex.com-b4c2a5f3ee5e43f818733226dbdb954e_l3.png "Rendered by QuickLaTeX.com")
, show that
Hint: try writing out what you’re given and contrast it with what you are attempting to show. 🙂
