Art of Problem Solving

1997 AIME Problems/Problem 14: Difference between revisions

Line 16: Line 16:
z^{1997}=1\\
z^{1997}=1\\
z^{1997}=e^{2\pi ik}\\
z^{1997}=e^{2\pi ik}\\
z=e^{\frac{2\pi ik}{1997}}<\math>
z=e^{\frac{2\pi ik}{1997}}</math>


== See also ==
== See also ==
* [[1997 AIME Problems]]
* [[1997 AIME Problems]]
</math>

Revision as of 19:13, 7 March 2007

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

See also