Question 1140741
<br>
{{{y = a*cos(b(x-c))+d}}}<br>
a is the amplitude
360/b degrees is the period
c is the positive phase shift  (that is, x-45 means shift 45 degrees to the right; x+60 (= x-(-60)) means shift 60 degrees to the left)
d is the vertical shift<br>
Put your function in that form by factoring out the coefficient of x:<br>
{{{y = 20*cos(9(x-9))-2}}}<br>
amplitude: a = 20
period: 360/b = 360/9 = 40 degrees
phase shift: c = 9 degrees to the right
vertical shift: d = -2, which means the axis (center line) is y=-2
domain: all reals
range: plus or minus 20 from the center line of -2, so -22 to +18