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Anastasia tried to solve the differential equation 
(dy)/(dx)=y^(2)sin(x). This is her work:

(dy)/(dx)=y^(2)sin(x)
Step 1: 
quad inty^(2)dy=int sin(x)dx
Step 2: 
quad(y^(3))/(3)=-cos(x)+C_(1)
Step 3: 
quady^(3)=-3cos(x)+C
Step 4: 
quad y=root(3)(-3cos(x)+C)
Is Anastasia's work correct? If not, what is her mistake?
Choose 1 answer:
(A) Anastasia's work is correct.
(B) Step 1 is incorrect. The separation of variables wasn't done correctly.
(C) Step 2 is incorrect. Anastasia didn't integrate 
sin(x) correctly.
(D) Step 4 is incorrect. The right-hand side of the equation should be 
root(3)(-cos(x))+C.

Anastasia tried to solve the differential equation dydx=y2sin(x) \frac{d y}{d x}=y^{2} \sin (x) . This is her work:\newlinedydx=y2sin(x) \frac{d y}{d x}=y^{2} \sin (x) \newlineStep 11: y2dy=sin(x)dx \quad \int y^{2} d y=\int \sin (x) d x \newlineStep 22: y33=cos(x)+C1 \quad \frac{y^{3}}{3}=-\cos (x)+C_{1} \newlineStep 33: y3=3cos(x)+C \quad y^{3}=-3 \cos (x)+C \newlineStep 44: y=3cos(x)+C3 \quad y=\sqrt[3]{-3 \cos (x)+C} \newlineIs Anastasia's work correct? If not, what is her mistake?\newlineChoose 11 answer:\newline(A) Anastasia's work is correct.\newline(B) Step 11 is incorrect. The separation of variables wasn't done correctly.\newline(C) Step 22 is incorrect. Anastasia didn't integrate sin(x) \sin (x) correctly.\newline(D) Step 44 is incorrect. The right-hand side of the equation should be cos(x)3+C \sqrt[3]{-\cos (x)}+C .

Full solution

Q. Anastasia tried to solve the differential equation dydx=y2sin(x) \frac{d y}{d x}=y^{2} \sin (x) . This is her work:\newlinedydx=y2sin(x) \frac{d y}{d x}=y^{2} \sin (x) \newlineStep 11: y2dy=sin(x)dx \quad \int y^{2} d y=\int \sin (x) d x \newlineStep 22: y33=cos(x)+C1 \quad \frac{y^{3}}{3}=-\cos (x)+C_{1} \newlineStep 33: y3=3cos(x)+C \quad y^{3}=-3 \cos (x)+C \newlineStep 44: y=3cos(x)+C3 \quad y=\sqrt[3]{-3 \cos (x)+C} \newlineIs Anastasia's work correct? If not, what is her mistake?\newlineChoose 11 answer:\newline(A) Anastasia's work is correct.\newline(B) Step 11 is incorrect. The separation of variables wasn't done correctly.\newline(C) Step 22 is incorrect. Anastasia didn't integrate sin(x) \sin (x) correctly.\newline(D) Step 44 is incorrect. The right-hand side of the equation should be cos(x)3+C \sqrt[3]{-\cos (x)}+C .
  1. Separating Variables: Anastasia starts by separating variables.\newline(dydx)=y2sin(x)(\frac{dy}{dx}) = y^{2}\sin(x)\newlineTo separate variables, we need to get all yy terms on one side and all xx terms on the other side.\newline(dyy2)=sin(x)dx(\frac{dy}{y^{2}}) = \sin(x)dx\newlineThis is the correct separation of variables.
  2. Integrating Both Sides: Anastasia integrates both sides.\newline(1/y2)dy=sin(x)dx\int(1/y^{2})dy = \int\sin(x)dx\newlineThe integral of 1/y21/y^2 with respect to yy is 1/y-1/y, and the integral of sin(x)\sin(x) with respect to xx is cos(x)-\cos(x).\newlineSo, 1/y=cos(x)+C1-1/y = -\cos(x) + C_1\newlineAnastasia's integration result is incorrect.

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