Skip to main content
Ch. 1 - Trigonometric Functions
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161, 9780135440780, 9780136881117, 9780135440827, 9780135924891Non è quello che usi tu?Cambia libro di testo
Capitolo 2, Problema 44

Concept Check Suppose that the point (x, y) is in the indicated quadrant. Determine whether the given ratio is positive or negative. Recall that r = √(x² + y²) .(Hint: Drawing a sketch may help.) III , r/y

Guida verificata passo dopo passo
1
Recall that the point (x, y) lies in Quadrant III, where both x and y coordinates are negative. This means x < 0 and y < 0 in this quadrant.
Remember the definition of r, which is the distance from the origin to the point (x, y), given by the formula \(r = \sqrt{x^2 + y^2}\). Since it is a distance, r is always positive regardless of the quadrant.
The ratio given is \(\frac{r}{y}\). Since r is positive and y is negative in Quadrant III, the numerator is positive and the denominator is negative.
When dividing a positive number by a negative number, the result is negative. Therefore, the ratio \(\frac{r}{y}\) will be negative in Quadrant III.
To confirm your understanding, sketch the coordinate plane, plot a point in Quadrant III, and visually verify the signs of x, y, and r, then consider the ratio \(\frac{r}{y}\).

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.
Durata del video:
2m

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Coordinate Plane Quadrants

The coordinate plane is divided into four quadrants, each with specific signs for x and y coordinates. In Quadrant III, both x and y values are negative. Understanding the sign of coordinates in each quadrant helps determine the sign of expressions involving x and y.
Video consigliato:
Percorso guidato
6:36
Quadratic Formula

Distance Formula and Radius r

The radius r is defined as r = √(x² + y²), representing the distance from the origin to the point (x, y). Since it is a distance, r is always positive regardless of the quadrant. This property is crucial when analyzing ratios involving r.
Video consigliato:
Percorso guidato
6:36
Quadratic Formula

Sign of Ratios Involving Coordinates

When evaluating the sign of a ratio like r/y, consider the signs of numerator and denominator separately. Since r is positive and y is negative in Quadrant III, the ratio r/y will be negative. This approach helps determine the positivity or negativity of trigonometric ratios.
Video consigliato:
Percorso guidato
05:32
Intro to Polar Coordinates