Science:Math Exam Resources/Courses/MATH220/December 2009/Question 07 (a)/Hint 1

Start writing down the first few terms:

$\displaystyle \cos(\pi /3)={\frac {1}{2}}$

$\displaystyle \cos(2\pi /3)={\frac {-1}{2}}$

$\displaystyle \cos(3\pi /3)=-1$

What will happen at $\displaystyle \cos(7\pi /3)$? Why? Can you use this to determine an answer?