Math Problem Statement

Sketch the curve r=2sinx

Solution

To sketch the curve for r=2sin(x)r = 2\sin(x) in polar coordinates, let's go through the key points.

Step-by-Step Guide:

  1. Understanding the Polar Equation:

    • In polar coordinates, the equation r=2sin(x)r = 2\sin(x) represents a relationship between the radial distance rr from the origin and the angle xx, which is the polar angle (in radians).
    • For each value of xx, rr gives the distance from the origin (pole).
  2. Key Features:

    • The curve repeats every 2π2\pi, since sin(x)\sin(x) has a period of 2π2\pi.
    • The values of rr vary depending on the angle xx. Specifically:
      • When x=0x = 0, r=0r = 0.
      • When x=π2x = \frac{\pi}{2}, r=2r = 2.
      • When x=πx = \pi, r=0r = 0.
      • When x=3π2x = \frac{3\pi}{2}, r=2r = -2 (meaning the point is plotted on the opposite side of the origin).
    • Since rr can be negative, the curve reflects across the origin for certain angles.
  3. Shape of the Curve:

    • The curve is symmetric about the polar axis (horizontal axis), and the resulting shape is known as a limacon.
    • It has an inner loop due to the negative values of rr.
  4. Plotting Important Points:

    • At x=0x = 0, r=0r = 0.
    • At x=π2x = \frac{\pi}{2}, r=2r = 2, so plot a point 2 units away from the origin.
    • At x=πx = \pi, r=0r = 0.
    • At x=3π2x = \frac{3\pi}{2}, r=2r = -2, meaning the point is 2 units away but on the opposite side of the origin.
  5. Final Shape:

    • The curve forms a limacon with no dimple and a loop. It starts at the origin, loops outward to a maximum of 2 units, and then reflects to form a symmetrical shape.

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Math Problem Analysis

Mathematical Concepts

Trigonometry
Polar Coordinates
Curve Sketching

Formulas

r = 2sin(x)
Sine function properties in polar coordinates

Theorems

Periodicity of the sine function
Symmetry in polar coordinates

Suitable Grade Level

Grades 10-12