Answer
$y=-0.71$, see explanations.
Work Step by Step
Step 1. See graph; it appears as a straight line $y=-0.71$
Step 2. We can explain the result in two ways: evaluate the function to obtain a constant or calculate the derivative of the function to get $f'(x)=0$
Step 3. $f'(x)=cos(x) sin(x+2)+sin(x) cos(x+2)-2sin(x+1)cos(x+1)=sin(x+2+x)-sin2(x+1)=0$, thus $f(x)=C$ where $C$ is a constant.
Step 4. Apply the trig product to the sum and half angle formulas, $f(x)=sin(x) sin(x+2)-sin^2(x+1)=\frac{1}{2}(cos(x+2-x)-cos(x+2+x))-\frac{1}{2}(1-cos2(x+1))=\frac{1}{2}(cos2-cos2(x+1))-\frac{1}{2}(1-cos2(x+1))=\frac{1}{2}cos2-\frac{1}{2}\approx-0.71$
