1997 AIME Problems/Problem 14

Revision as of 20:06, 7 March 2007 by Ninja glace (talk | contribs) (Solution)

Problem

Let $\displaystyle v$ and $\displaystyle w$ be distinct, randomly chosen roots of the equation $\displaystyle z^{1997}-1=0$. Let $\displaystyle \frac{m}{n}$ be the probability that $\displaystyle\sqrt{2+\sqrt{3}}\le\left|v+w\right|$, where $\displaystyle m$ and $\displaystyle n$ are relatively prime positive integers. Find $\displaystyle m+n$.

Solution

The solution requires the use of Euler's formula:

$\displaystyle e^{i\theta}=\cos(\theta)+i\sin(\theta)$

If $\displaystyle \theta=2\pi ik$, where k is any constant, the equation reduces to: \begin{eqnarray*} e^{2\pi ik}&=&\cos(2\pi k)+i\sin(2\pi k) &=&1+0i &=&1+0 &=&1 \end{eqnarray*}

See also