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Ch. 2 - Acute Angles and Right Triangles
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161Not the one you use?Change textbook
Chapter 3, Problem 2.5.18

Concept Check The two methods of expressing bearing can be interpreted using a rectangular coordinate system. Suppose that an observer for a radar station is located at the origin of a coordinate system. Find the bearing of an airplane located at each point. Express the bearing using both methods. (2, 2)

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Identify the position of the airplane relative to the radar station at the origin. The coordinates given are (2, 2), which means the airplane is 2 units east and 2 units north of the radar station.
Calculate the angle \( \theta \) that the line from the origin to the point (2, 2) makes with the positive x-axis (east direction) using the tangent function: \( \tan(\theta) = \frac{y}{x} = \frac{2}{2} \).
Find \( \theta \) by taking the arctangent (inverse tangent) of \( \frac{2}{2} \), which gives the angle in degrees or radians measured counterclockwise from the positive x-axis.
Express the bearing in the first method (the compass bearing) by converting the angle \( \theta \) to a compass bearing, which is typically measured clockwise from the north (positive y-axis). Since \( \theta \) is measured from east, use the relationship: \( \text{bearing} = 90^\circ - \theta \).
Express the bearing in the second method (the azimuth bearing) as the angle \( \theta \) measured clockwise from the north direction, or equivalently, the angle from the positive y-axis to the point, which can be found by adjusting \( \theta \) accordingly.

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Key Concepts

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

Bearing and Its Methods

Bearing is a way to describe direction relative to a reference direction, usually north. The two common methods are the compass bearing, measured clockwise from north (0° to 360°), and the quadrant bearing, expressed as an angle east or west of north or south (e.g., N45°E). Understanding both methods is essential to convert and interpret directions accurately.
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Rectangular Coordinate System and Position Vectors

In a rectangular coordinate system, points are represented by (x, y) coordinates relative to the origin. The position vector from the origin to a point defines the direction and distance of the object. This system helps translate spatial locations into angles and distances, which are necessary for calculating bearings.
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Calculating Angles Using Trigonometric Functions

To find the bearing from coordinates, use trigonometric functions like tangent to calculate the angle between the position vector and the reference axis (usually the positive y-axis for north). The arctangent function helps determine the angle from the x and y coordinates, which can then be converted into the appropriate bearing format.
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