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If x(t)=3cos^(2)t and y(t)=-3sin t, eliminate the parameter to write the parametric equations as a Cartesian equation.
Select the correct answer below:
(A) y^(2)=9-3x
(B) x^(2)=9-3y
(C) (x^(2))/(9)+(y^(2))/(9)=1
(D) (x)/(3)-(y)/(3)=1

If x(t)=3cos2t x(t)=3 \cos ^{2} t and y(t)=3sint y(t)=-3 \sin t , eliminate the parameter to write the parametric equations as a Cartesian equation.\newlineSelect the correct answer below:\newline(A) y2=93x y^{2}=9-3 x \newline(B) x2=93y x^{2}=9-3 y \newline(C) x29+y29=1 \frac{x^{2}}{9}+\frac{y^{2}}{9}=1 \newline(D) x3y3=1 \frac{x}{3}-\frac{y}{3}=1

Full solution

Q. If x(t)=3cos2t x(t)=3 \cos ^{2} t and y(t)=3sint y(t)=-3 \sin t , eliminate the parameter to write the parametric equations as a Cartesian equation.\newlineSelect the correct answer below:\newline(A) y2=93x y^{2}=9-3 x \newline(B) x2=93y x^{2}=9-3 y \newline(C) x29+y29=1 \frac{x^{2}}{9}+\frac{y^{2}}{9}=1 \newline(D) x3y3=1 \frac{x}{3}-\frac{y}{3}=1
  1. Given Equations: Given the parametric equations:\newlinex(t)=3cos2(t)x(t) = 3\cos^2(t)\newliney(t)=3sin(t)y(t) = -3\sin(t)\newlineWe want to eliminate the parameter tt to find a Cartesian equation that relates xx and yy.
  2. Pythagorean Identity: We know that sin2(t)+cos2(t)=1\sin^2(t) + \cos^2(t) = 1 from the Pythagorean identity.
  3. Expressing cos2(t)\cos^2(t): We can express cos2(t)\cos^2(t) in terms of xx by rearranging the equation for x(t)x(t):
    x=3cos2(t)x = 3\cos^2(t)
    cos2(t)=x3\cos^2(t) = \frac{x}{3}
  4. Expressing sin(t)\sin(t): Similarly, we can express sin(t)\sin(t) in terms of yy by rearranging the equation for y(t)y(t):
    y=3sin(t)y = -3\sin(t)
    sin(t)=y3\sin(t) = -\frac{y}{3}
  5. Squaring sin(t): Now we square both sides of the equation for sin(t)sin(t) to get sin2(t)sin^2(t):sin2(t)=(y3)2sin^2(t) = \left(-\frac{y}{3}\right)^2sin2(t)=y29sin^2(t) = \frac{y^2}{9}
  6. Substitute into Identity: Substitute cos2(t)\cos^2(t) and sin2(t)\sin^2(t) into the Pythagorean identity:\newlinesin2(t)+cos2(t)=1\sin^2(t) + \cos^2(t) = 1\newline(y29)+(x3)=1(\frac{y^2}{9}) + (\frac{x}{3}) = 1
  7. Clearing Denominators: Multiply through by 99 to clear the denominators: 9(y29)+9(x3)=9(1)9\left(\frac{y^2}{9}\right) + 9\left(\frac{x}{3}\right) = 9(1) y2+3x=9y^2 + 3x = 9
  8. Rearranging Equation: Rearrange the equation to match the answer choices: y2=93xy^2 = 9 - 3x

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