1000 mL = 1 L
0.85 L = (0.85 L)*(1000 mL/1 L) = (0.85*1000) mL = 850 mL
So, 0.85 liters is equivalent to 850 milliliters
A cosine is just a sine shifted to the left by π/2. A cosine of 4x is shifted to the left by only π/8 because of the factor 4. Sketch them.
The region we're looking for is this sausage-shaped part between the cos and the sin.
The x intercepts are at π/8 for the cosine and π/4 for the sine. The midpoint between them is at (π/8 + π/4)/2 = 3/16π.
The region is point symmetric around the x axis, so the y coordinate of the centroid is 0.
So the centroid is at (3/16π, 0)
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