Ch. 5 - Complex Numbers, Polar Coordinates and Parametric Equations

Blitzer3rd EditionTrigonometryISBN: 9780137316601Not the one you use?Change textbook

Blitzer 3rd Edition

Ch. 5 - Complex Numbers, Polar Coordinates and Parametric Equations

Problem 5.3.45

Chapter 5, Problem 5.3.45

In Exercises 41–48, the rectangular coordinates of a point are given. Find polar coordinates of each point. Express θ in radians. (−√3,−1)

Verified step by step guidance

Recall that to convert rectangular coordinates \((x, y)\) to polar coordinates \((r, \theta)\), we use the formulas: \(r = \sqrt{x^2 + y^2}\) and \(\theta = \arctan\left(\frac{y}{x}\right)\).

Calculate the radius \(r\) by substituting \(x = -\sqrt{3}\) and \(y = -1\) into the formula: \(r = \sqrt{(-\sqrt{3})^2 + (-1)^2}\).

Find the initial angle \(\theta\) by computing \(\arctan\left(\frac{y}{x}\right) = \arctan\left(\frac{-1}{-\sqrt{3}}\right)\), which simplifies to \(\arctan\left(\frac{1}{\sqrt{3}}\right)\).

Determine the correct quadrant for \(\theta\). Since both \(x\) and \(y\) are negative, the point lies in the third quadrant, so adjust \(\theta\) accordingly by adding \(\pi\) radians to the reference angle.

Express the final polar coordinates as \((r, \theta)\) with \(r\) positive and \(\theta\) in radians, ensuring \(\theta\) is between \(0\) and \(2\pi\).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Rectangular and Polar Coordinates

Rectangular coordinates (x, y) represent a point's position on the Cartesian plane using horizontal and vertical distances. Polar coordinates (r, θ) describe the same point by its distance r from the origin and the angle θ it makes with the positive x-axis, measured in radians.

Conversion Formulas Between Coordinates

To convert from rectangular to polar coordinates, use r = √(x² + y²) to find the radius and θ = arctan(y/x) to find the angle. Adjust θ based on the quadrant of the point to ensure the angle correctly represents the point's direction.

Angle Measurement in Radians and Quadrant Considerations

Angles in polar coordinates are measured in radians, where 2π radians equal 360°. Since arctan(y/x) returns values between -π/2 and π/2, you must consider the signs of x and y to determine the correct quadrant and adjust θ accordingly for accurate representation.

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