Thread: Find a Trigonometric equation

Give an equation for a cosine funtion that has a maximum at (pi/4, 8), followed immediately by another maximum at (9pi/4,8), and has a minimum at value of 4.

This is what I did

Amplitude = (8-4)/2
= 2

Vertical shift = 8-2 =6

So far I got this
y = 2cos (x -? )+6

How do I find the phase shift

The cosine function normally has consecutive maximums at and . Your function has consecutive maximums at and . This means the period is , which is normal for the cosine function. So what is the phase shift when you move to ?