the answers 16 if you need an explanation then ill comment one.....!
Answer:
The relationship between the circumference of a circle and its diameter represent a direct variation and the constant of proportionality is equal to the constant 
Step-by-step explanation:
we know that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form 
where K is the constant of proportionality
In this problem we know that
The circumference of a circle is equal to

therefore
the relationship between the circumference of a circle and its diameter is a direct variation and the constant of proportionality is equal to the constant 
I would say c but that is just a guess
Answer:
y = cos(x) -1
Step-by-step explanation:
The function has a maximum at x=0, a peak-to-peak amplitude of 2, and a period of 2π. It matches a cosine function that has been shifted down 1 unit.
y = cos(x) -1
It can be solved by factoring or taking the root of both sides.
x= 2 radical 3. and -2 radical 3