Math Problem Statement

solve this Prompt: how many times does $r = 2 + sin(\theta)$ pass through x = 1 in cartesian coordinates? then learn it

Solution

To solve the problem of determining how many times the polar curve r=2+sin(θ)r = 2 + \sin(\theta) passes through x=1x = 1 in Cartesian coordinates, we need to translate this equation into the Cartesian system and then find the values of θ\theta that satisfy the condition x=1x = 1.

Step 1: Express the Polar Equation in Cartesian Coordinates

In polar coordinates, the relationship between rr and Cartesian coordinates (x,y)(x, y) is given by: x=rcos(θ)andy=rsin(θ)x = r \cos(\theta) \quad \text{and} \quad y = r \sin(\theta) Given r=2+sin(θ)r = 2 + \sin(\theta), we substitute this into the expression for xx: x=(2+sin(θ))cos(θ)x = (2 + \sin(\theta)) \cos(\theta) Now we want to find how many times this equation satisfies x=1x = 1, so we set: 1=(2+sin(θ))cos(θ)1 = (2 + \sin(\theta)) \cos(\theta) This is the equation we need to solve for θ\theta.

Step 2: Solve the Equation

We now have: 1=(2+sin(θ))cos(θ)1 = (2 + \sin(\theta)) \cos(\theta) Expanding and rearranging the equation, we get: cos(θ)=12+sin(θ)\cos(\theta) = \frac{1}{2 + \sin(\theta)} This equation needs to be solved for θ\theta, and we will need to check how many values of θ\theta satisfy this equation over the range θ[0,2π]\theta \in [0, 2\pi].

Step 3: Analyze the Equation

The equation cos(θ)=12+sin(θ)\cos(\theta) = \frac{1}{2 + \sin(\theta)} is transcendental, so we can solve it by analyzing it graphically or numerically. However, we can infer the general behavior by considering:

  1. Domain of the Equation: The right-hand side of the equation, 12+sin(θ)\frac{1}{2 + \sin(\theta)}, is always positive and lies between 13\frac{1}{3} (when sin(θ)=1\sin(\theta) = 1) and 12\frac{1}{2} (when sin(θ)=0\sin(\theta) = 0).
  2. Periodicity of Trigonometric Functions: Since both sin(θ)\sin(\theta) and cos(θ)\cos(\theta) are periodic with a period of 2π2\pi, the equation could potentially have multiple solutions within a single period.

Step 4: Find Number of Solutions

Numerical or graphical analysis shows that this equation has two distinct solutions within the interval [0,2π][0, 2\pi]. Therefore, the curve r=2+sin(θ)r = 2 + \sin(\theta) passes through x=1x = 1 twice.

Conclusion

The curve r=2+sin(θ)r = 2 + \sin(\theta) passes through x=1x = 1 in Cartesian coordinates 2 times.


Would you like to go over any specific steps in detail or have any further questions?

Here are 5 related questions you could explore:

  1. What is the geometric interpretation of polar curves in the Cartesian plane?
  2. How do you find the points where a polar curve intersects the x-axis?
  3. What are some general methods for solving transcendental equations like this one?
  4. How does the behavior of trigonometric functions affect the number of solutions in equations like this?
  5. How can graphical or numerical methods be applied to solve trigonometric equations?

Tip: For transcendental equations involving sine and cosine, graphical analysis often helps reveal how many solutions exist across specific intervals.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Polar Coordinates
Cartesian Coordinates
Trigonometric Equations
Transcendental Equations

Formulas

x = r \cos(\theta)
y = r \sin(\theta)
r = 2 + \sin(\theta)

Theorems

Polar to Cartesian Transformation
Trigonometric Identities

Suitable Grade Level

Grades 10-12