## Algebra and Trigonometry 10th Edition

$f(t)$ and $f(\frac{1}{2}t)$ have different peiods: $c$ and $2c$. So, the property $f(t+c)=f(t)$ can not be applied. Also, $f(t+\frac{1}{2}c)=f(t-\frac{1}{2}c)\ne f(\frac{1}{2}t)$