# What is the period of f(t)=sin( ( 6 t) /7 +pi/4 )?

$7 \frac{\pi}{3}$
The$\sin \left(k \left(t + 2 n \frac{\pi}{k}\right) + l\right) = \sin \left(k t + l\right)$, n=+-1.+-2,+-3,..,.
The value repeats when t is increased by $2 \frac{\pi}{k}$. This is the period.
Here, $k = \frac{6}{7}$.
So, the period of f(t) is $7 \frac{\pi}{3}$..