Math Problem Statement

Find an ordered pair of polar coordinates to represent the point whose rectangular coordinates are (-3,4)

Solution

To find the polar coordinates for the point (3,4)(-3, 4) in rectangular form, we need to convert it to the form (r,θ)(r, \theta), where:

  • rr is the radial distance (distance from the origin),
  • θ\theta is the angle (measured counterclockwise from the positive x-axis).

Step 1: Calculate the radial distance rr

The radial distance rr is given by the formula: r=x2+y2r = \sqrt{x^2 + y^2} where x=3x = -3 and y=4y = 4.

Substitute the values of xx and yy: r=(3)2+42=9+16=25=5r = \sqrt{(-3)^2 + 4^2} = \sqrt{9 + 16} = \sqrt{25} = 5 So, r=5r = 5.

Step 2: Calculate the angle θ\theta

The angle θ\theta can be found using the inverse tangent function, considering the quadrant the point lies in.

The angle is calculated by: θ=tan1(yx)\theta = \tan^{-1}\left(\frac{y}{x}\right) For x=3x = -3 and y=4y = 4, the ratio yx=43=43\frac{y}{x} = \frac{4}{-3} = -\frac{4}{3}.

Using a calculator, we find: θ=tan1(43)53.13\theta = \tan^{-1}\left(-\frac{4}{3}\right) \approx -53.13^\circ

However, the point (3,4)(-3, 4) lies in the second quadrant, where the angle is positive. To adjust for this, we add 180180^\circ to the calculated angle: θ=53.13+180=126.87\theta = -53.13^\circ + 180^\circ = 126.87^\circ

Thus, the polar coordinates for the point (3,4)(-3, 4) are approximately: (r,θ)=(5,126.87)(r, \theta) = (5, 126.87^\circ)

Final Answer:

The polar coordinates of the point (3,4)(-3, 4) are (5,126.87)(5, 126.87^\circ).

Would you like further explanation on this? Feel free to ask if something is unclear!


Related questions:

  1. How do you convert polar coordinates back to rectangular coordinates?
  2. How do you determine the quadrant in which a point lies based on its rectangular coordinates?
  3. What is the general form for expressing polar coordinates?
  4. How do you calculate the angle in polar coordinates when the point lies on the x-axis or y-axis?
  5. How does the sign of rr affect the representation of polar coordinates?

Tip: Remember that angles in polar coordinates are usually expressed in degrees or radians. Ensure you are consistent with the unit used for θ\theta.

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Math Problem Analysis

Mathematical Concepts

Polar Coordinates
Rectangular Coordinates
Trigonometry

Formulas

r = √(x² + y²)
θ = tan⁻¹(y/x)

Theorems

Conversion between polar and rectangular coordinates

Suitable Grade Level

Grades 9-12