+129771 We have the form
y = A cos (B (x - D)) + C
A = the amplitude = [ 3 - - 11] / 2 = 14 / 2 = 7
C= the midline = [ 3 - 11 ] / 2 = -8 / 2 = -4
The period = [ ((5/2)pi + 2 pi)) / 2 - pi/4 ] = [ (10/4)pi + (8/4)pi ) / 2 - pi/4] =
[ (18/4)pi / 2 - pi/ 4] = [ (18/8)pi - pi/4 ] = [ (9/4)pi - pi/4 ] = (8/4)pi = 2pi
B = 2pi / period = 2pi / 2pi = 1
D = the phase shift = pi/4
The equation is
y = 7cos ( x - pi/4) - 4
See here :
