Graphing  Trigonometry
posted by Sam .
Below is the graph of y = a cos(bx+c)+d, where a, b, and c are positive, and c is as small as possible. Find a + b + c + d.
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The link is to a screenshot of the graph. (without spaces)
I'm unsure of how to solve  I tried it and got y = 2 cos (2/3x + 5pi/2) + 1 but it is wrong....help would be appreciated, thanks.

maxmin = 4, so a=2
center of wave is at y=1, so d=1
period is 3pi, so b=2/3
wave is shifted right by 3pi/2, so we have 2/3 (x3pi/2) = 2/3 x  pi
y = 2cos(2/3 x  pi) + 1 
thanks a lot man :)

thanks a lot steve you're awesome and helping me a lot on these problems I've tried working on them and when I couldn't you helped me so thanks