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Ch. 7 - Applications of Trigonometry and Vectors
Lial - Trigonometry 12th Edition
Lial12th EditionTrigonometryISBN: 9780136552161, 9780135440780, 9780136881117, 9780135440827, 9780135924891Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 51

Find the area of each triangle ABC.
A = 42.5°, b = 13.6 m, c = 10.1 m

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Identify the given elements of the triangle: angle \(A = 42.5^\circ\), side \(b = 13.6\) m, and side \(c = 10.1\) m. We need to find the area of triangle \(ABC\).
Recall the formula for the area of a triangle when two sides and the included angle are known: \(\text{Area} = \frac{1}{2} \times b \times c \times \sin(A)\).
Substitute the known values into the formula: \(\text{Area} = \frac{1}{2} \times 13.6 \times 10.1 \times \sin(42.5^\circ)\).
Calculate \(\sin(42.5^\circ)\) using a calculator or trigonometric table to find the sine of the given angle.
Multiply the values together: half of the product of sides \(b\) and \(c\), then multiply by \(\sin(42.5^\circ)\) to find the area of the triangle.

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Law of Cosines

The Law of Cosines relates the lengths of the sides of a triangle to the cosine of one of its angles. It is useful for finding an unknown side or angle when two sides and the included angle are known. The formula is c² = a² + b² - 2ab cos(C), helping to determine missing elements in non-right triangles.
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Intro to Law of Cosines

Area of a Triangle Using Two Sides and Included Angle

The area of a triangle can be calculated using two sides and the included angle with the formula: Area = 1/2 * b * c * sin(A). This method is especially useful when the height is unknown but two sides and the angle between them are given, allowing direct computation of the area.
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Calculating Area of SAS Triangles

Sine Function in Trigonometry

The sine function relates an angle of a triangle to the ratio of the length of the opposite side over the hypotenuse in a right triangle. In non-right triangles, sine is used in formulas like the area formula and the Law of Sines, making it essential for solving problems involving angles and side lengths.
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Introduction to Trigonometric Functions
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