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Ch.12 - Parametric and Polar Curves
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 12, Problem 12.2.28

25–30. Converting coordinates Express the following polar coordinates in Cartesian coordinates.


(2, 7π/4)

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1
Recall the formulas to convert polar coordinates \((r, \theta)\) to Cartesian coordinates \((x, y)\): \(x = r \cos(\theta)\) \(y = r \sin(\theta)\)
Identify the given polar coordinates: \(r = 2\) \(\theta = \frac{7\pi}{4}\)
Substitute the values into the conversion formulas: \(x = 2 \cos\left(\frac{7\pi}{4}\right)\) \(y = 2 \sin\left(\frac{7\pi}{4}\right)\)
Evaluate the trigonometric functions \(\cos\left(\frac{7\pi}{4}\right)\) and \(\sin\left(\frac{7\pi}{4}\right)\) using the unit circle or known values for these angles.
Multiply the results by \(r = 2\) to find the Cartesian coordinates \((x, y)\).

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Key Concepts

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

Polar Coordinates

Polar coordinates represent a point in the plane using a distance from the origin (radius r) and an angle θ measured from the positive x-axis. They are expressed as (r, θ), where r ≥ 0 and θ is typically in radians.
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Intro to Polar Coordinates

Conversion Formulas from Polar to Cartesian Coordinates

To convert polar coordinates (r, θ) to Cartesian coordinates (x, y), use the formulas x = r cos(θ) and y = r sin(θ). These relate the radius and angle to the horizontal and vertical distances from the origin.
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Intro to Polar Coordinates

Trigonometric Values for Common Angles

Understanding the sine and cosine values of common angles, such as 7π/4, is essential for conversion. For example, cos(7π/4) = √2/2 and sin(7π/4) = -√2/2, which help compute exact Cartesian coordinates.
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Introduction to Trigonometric Functions