## 22 April 2018

### One half

Some mathematical operations whose result is $\frac{1}{2}$:

• $\cos 60º = \frac{1}{2}$;
• $\frac{\cos 30º}{\sqrt 3}=\frac{1}{2}$;
• $\frac{1}{3}+\frac{1}{6}=\frac{1}{2}$.
Using all the digits from $1$ to $9$:
• $\frac{6,729}{13,458}=\frac{1}{2}$.
Using the same number twice but changing the position of one digit:
• $\frac{105,263,157,894,736,842}{210,526,315,789,473,684}=\frac{1}{2}$.
Numbers with such property are called parasitic numbers.