posted by Tabby .
Write the equation of the cosine function with an amplitude of 1, a period of 3pi/7, a phase shift of -pi/5, and a vertical shift of 2 units down.
The only actual calculation you have to do deals witht the period.
period = 2π/k
3π/7 = 2π/k
I am also not clear about your information re phase shift,
I will assume that by " a phase shift of -π/5" you mean a shift of π/5 to the left.
If you meant the opposite, just change the sign for the phase shift in my answer.
y = cos(14/3)(Ø + π/5) - 2
i didn't mean to put a negative sign