The equation correspond to the graph is
.
Observe the graph :
\The distance from the maximum to the minimum value of the function is 
Half of the distance from the maximum to the minimum value of the function is
.
So the amplitude is
.
Period 
Here the function completes one period on
.
Substitute Period
in Period
.

The midline appears at
, there is no vertical shift.
Since the midline appears at
, the value of
is zero.
Since there is no vertical shift, the value of
is zero.
Substitute
,
,
and
.

The equation correspond to the graph is
.
The equation correspond to the graph is
.