1997 AIME Problems/Problem 14

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: $e^{2\pi ik}=\cos(2\pi k)+i\sin(2\pi k)\\ =1+0i\\ =1+0\\ =1\\ z^{1997}-1=0\\ z^{1997}=1\\ z^{1997}=e^{2\pi ik}\\ z=e^{\frac{2\pi ik}{1997}}$

Page

Toolbox

Search

1997 AIME Problems/Problem 14

Problem

Solution

See also