Math Problem Statement

Find an equation in cylindrical coordinates for the surface represented by the rectangular equation y = x^2.

Solution

To convert the equation y=x2y = x^2 from rectangular coordinates to cylindrical coordinates, we use the relationships between rectangular coordinates (x,y,z)(x, y, z) and cylindrical coordinates (r,θ,z)(r, \theta, z). The transformations are:

  • x=rcosθx = r \cos \theta
  • y=rsinθy = r \sin \theta
  • z=zz = z

Given the equation: y=x2y = x^2

Step 1: Substitute xx and yy in terms of cylindrical coordinates.

Since x=rcosθx = r \cos \theta and y=rsinθy = r \sin \theta, substitute these values: rsinθ=(rcosθ)2r \sin \theta = (r \cos \theta)^2

Step 2: Simplify the equation.

Expanding (rcosθ)2(r \cos \theta)^2: rsinθ=r2cos2θr \sin \theta = r^2 \cos^2 \theta

Step 3: Divide both sides by rr (assuming r0r \neq 0).

sinθ=rcos2θ\sin \theta = r \cos^2 \theta

This is the equation in cylindrical coordinates that corresponds to the given rectangular equation y=x2y = x^2.

Would you like further details on this solution, or do you have any questions?

Here are some related questions you might consider:

  1. How would you convert other rectangular equations like x=y2x = y^2 to cylindrical coordinates?
  2. What happens if the equation includes zz in rectangular coordinates? How do we handle that in cylindrical coordinates?
  3. Can you convert x2+y2=1x^2 + y^2 = 1 into cylindrical coordinates?
  4. How do spherical coordinates differ from cylindrical coordinates in such conversions?
  5. How would you find the surface or volume bounded by a cylindrical coordinate equation?

Tip: Always double-check the transformation equations when switching between coordinate systems, as minor errors can lead to incorrect results.

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Math Problem Analysis

Mathematical Concepts

Coordinate Transformation
Cylindrical Coordinates
Rectangular Coordinates

Formulas

x = r * cos(θ)
y = r * sin(θ)

Theorems

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Suitable Grade Level

College level