Math Problem Statement

Express the following ellipses in general form and sketch its graphs.

Express the following ellipses in general form and sketch its graphs.

Solution

You provided the parametric equations:

x=3cosθ+3,y=5sinθ5x = 3\cos\theta + 3, \quad y = 5\sin\theta - 5

Step 1: Eliminate the parameter θ\theta

We aim to express this as an equation in terms of xx and yy. Begin by isolating cosθ\cos\theta and sinθ\sin\theta in the parametric equations:

  1. From x=3cosθ+3x = 3\cos\theta + 3: cosθ=x33\cos\theta = \frac{x - 3}{3}

  2. From y=5sinθ5y = 5\sin\theta - 5: sinθ=y+55\sin\theta = \frac{y + 5}{5}

Step 2: Use the identity sin2θ+cos2θ=1\sin^2\theta + \cos^2\theta = 1

Substitute the expressions for cosθ\cos\theta and sinθ\sin\theta into the identity:

(x33)2+(y+55)2=1\left(\frac{x - 3}{3}\right)^2 + \left(\frac{y + 5}{5}\right)^2 = 1

Step 3: Simplify

Expand the terms:

(x3)29+(y+5)225=1\frac{(x - 3)^2}{9} + \frac{(y + 5)^2}{25} = 1

This is the equation of an ellipse in standard form:

(x3)29+(y+5)225=1\frac{(x - 3)^2}{9} + \frac{(y + 5)^2}{25} = 1

Step 4: Analyze the Ellipse

  • The center of the ellipse is at (3,5)(3, -5).
  • The semi-major axis is 5 (since 25=5225 = 5^2).
  • The semi-minor axis is 3 (since 9=329 = 3^2).

This is a vertically oriented ellipse because the semi-major axis is along the yy-axis.

Step 5: Sketch the Graph

To sketch the ellipse:

  1. Plot the center at (3,5)(3, -5).
  2. From the center, move 5 units up and down along the yy-axis (since the semi-major axis is 5).
  3. Move 3 units left and right along the xx-axis (since the semi-minor axis is 3).
  4. Draw the ellipse through these points.

Would you like me to generate a detailed graph for this ellipse, or provide further details on the derivation?

Follow-up Questions:

  1. Can you describe the key characteristics of an ellipse based on its equation?
  2. How do we interpret the semi-major and semi-minor axes of an ellipse?
  3. What is the importance of the center in the standard form of an ellipse?
  4. How does the orientation of the axes affect the shape of the ellipse?
  5. What is the effect of changing the coefficients in the equation of the ellipse?

Tip:

Always remember that the semi-major axis is the longest diameter of the ellipse, and the semi-minor axis is the shortest.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Parametric Equations
Conic Sections
Ellipses

Formulas

x = 3cos(θ) + 3
y = 5sin(θ) - 5
cos^2(θ) + sin^2(θ) = 1
(x - h)^2 / a^2 + (y - k)^2 / b^2 = 1

Theorems

Trigonometric Identity: sin^2(θ) + cos^2(θ) = 1

Suitable Grade Level

Grades 10-12