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Lyra is designing a model of a solar system with a planet and a comet. The planet has a circular orbit, centered at the origin with a diameter of 140. The comet follows a parabolic path with directrix x = 100 and vertex at (85, 0). Part A: Write the equation of the planet's orbit in standard form. Show your work. (2 points) Part B: Write the equation of the comet's path in standard form. Show your work. (4 points) Part C: Identify all points where the planet's orbit intersects the path of the comet. Show your work and round answers to the hundredths place. (4 points)

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Answer:

Part A: The equation of the planet's orbit is simply the equation of a circle with radius 70 (half the diameter) and center at the origin. The standard form equation of a circle with radius r and center at (h,k) is (x-h)^2 + (y-k)^2 = r^2. In this case, h and k are both 0, so the equation of the planet's orbit is simply x^2 + y^2 = 70^2.

Part B: The equation of the comet's path is a parabola with directrix x=100 and vertex at (85, 0). The standard form equation of a parabola with directrix x=p, vertex at (h,k), and focus at (h,k+f) is y = (4f/p^2)(x-h)^2 + k. In this case, p=100, h=85, k=0, and f is the distance from the vertex to the focus. We can find f by using the equation f = sqrt(p^2+4ah), where a is the distance from the vertex to the directrix. In this case, a=50, so f = sqrt(100^2+45085) = 50. Plugging this value into the equation for the parabola, we get y = (4*50/100^2)(x-85)^2 + 0. Simplifying this gives us y = (2/25)(x-85)^2.

Part C: To find the points where the planet's orbit intersects the path of the comet, we need to find the points where the x and y coordinates of the two equations are equal. Setting the two equations equal to each other gives us (2/25)(x-85)^2 = x^2 + y^2 - 70^2. Expanding the left side and rearranging the terms gives us x^2 - 170x + 15129 = 0. We can use the quadratic formula to find the solutions for x: x = (170 +/- sqrt(170^2 - 4115129))/2. This simplifies to x = 85 +/- sqrt(40900). Therefore, the points of intersection are (85 + sqrt(40900), 0) and (85 - sqrt(40900), 0). Rounding these values to the hundredths place gives us (92.84, 0) and (77.16, 0).

User Denys Kurochkin
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