Math Problem Statement

x=3cos(theta)+1, y=4sin(theta)-2, eliminate the parameter

Solution

To eliminate the parameter θ\theta from the parametric equations x=3cos(θ)+1x = 3\cos(\theta) + 1 and y=4sin(θ)2y = 4\sin(\theta) - 2, we want to find a relationship between xx and yy that doesn't involve θ\theta.

Here's the step-by-step process:

  1. Express cos(θ)\cos(\theta) and sin(θ)\sin(\theta) in terms of xx and yy:

    • From the first equation, solve for cos(θ)\cos(\theta): x=3cos(θ)+1    cos(θ)=x13x = 3\cos(\theta) + 1 \implies \cos(\theta) = \frac{x - 1}{3}
    • From the second equation, solve for sin(θ)\sin(\theta): y=4sin(θ)2    sin(θ)=y+24y = 4\sin(\theta) - 2 \implies \sin(\theta) = \frac{y + 2}{4}
  2. Use the Pythagorean identity:

    • Recall the identity: cos2(θ)+sin2(θ)=1\cos^2(\theta) + \sin^2(\theta) = 1.
    • Substitute the expressions found for cos(θ)\cos(\theta) and sin(θ)\sin(\theta): (x13)2+(y+24)2=1\left(\frac{x - 1}{3}\right)^2 + \left(\frac{y + 2}{4}\right)^2 = 1
  3. Simplify the equation:

    • Expand and simplify: (x1)29+(y+2)216=1\frac{(x - 1)^2}{9} + \frac{(y + 2)^2}{16} = 1

This is the equation of an ellipse with its center at (1,2)(1, -2), a horizontal semi-axis length of 3, and a vertical semi-axis length of 4.

Summary: The Cartesian equation of the curve is: (x1)29+(y+2)216=1\frac{(x - 1)^2}{9} + \frac{(y + 2)^2}{16} = 1

Would you like a more detailed explanation or have any questions?

Here are some related questions you might find interesting:

  1. What are the general steps for eliminating parameters from parametric equations?
  2. How can we determine the type of conic section given its Cartesian equation?
  3. How do you find the center and axes lengths of an ellipse from its equation?
  4. How would the equations change if θ\theta was eliminated using different trigonometric identities?
  5. Can you eliminate the parameter θ\theta for parametric equations of a hyperbola or parabola?

Tip: When eliminating parameters, always look for trigonometric identities or algebraic manipulation to link the variables directly without the parameter.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Parametric Equations
Ellipse

Formulas

x = 3cos(θ) + 1
y = 4sin(θ) - 2
cos^2(θ) + sin^2(θ) = 1
Equation of an ellipse: (x - h)^2/a^2 + (y - k)^2/b^2 = 1

Theorems

Pythagorean Identity

Suitable Grade Level

Grades 10-12