x | -120° | -60° | 0° | 60° | 120° | 180° | 240° |
-----------------------------------------------------
y | 1.5 | 3 | 1.5 | 0 | 1.5 | 3 | 1.5 |
This is the graph:
The equation is
where |A| = amplitude = (maximum value - minimum value)/2 = (3-0)/2 = 3/2,
So we substitute 3/2 for A
The period = 360°/B = length of one cycle. The first cycle goes from
-120° to 120° which is 120°-(-120°) = 120°+120° = 240°
So 360°/B = 240°
360° = 240°B
360°/240° = B
3/2 = B
We substitute 3/2 for B:
The phase (horizontal) shift, as we can tell from the graph, is 120° LEFT,
so C/B is +120°. (+ if left, and - if right)
C/B = 120°
C = 120°B
C = 120°(3/2)
C = 180°
We substitute 180° for C
Finally the vertical shift is D and we can see that the graph has a
vertical shift upward of 1.5, so we substitute 1.5 for D:
And since 1.5 = 3/2 we can just write 3/2 for 1.5 and all the
constants just happened to came out to be 3/2.
Edwin