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Learn about sine, cosine, and tangent ratios in right triangles with practical examples and applications. Understand angle of elevations, depressions, and how to solve trigonometric equations.
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Chapter 13 Sec 1 Right Triangle Trigonometry
Trigonometric Ratios • The ratios of the sides of the right triangle can be used to define the trigonometric ratios. • The ratio of the side opposite θand the hypotenuse is known as sine. • The ratio of the side adjacent θ and the hypotenuse is known as cosine. • The ratio of the side opposite θ and the side adjacent θ is known as tangent.
Right Triangle Trigonometry • Let’s consider a right triangle, one of whose acute angles is θ • The three sides of the triangle are the hypotenuse, the side oppositeθ, and the side adjacent to θ . opposite hypotenuse SOH CAH TOA adjacent
Example 1 Find the values of the sine, cosine, and tangent for A. First find the length of AC. (AB)2 + (BC)2 = (AC)2 152 + 82 = 289 = (AC)2 AC = 17 C 8 cm B 15 cm A 17 cm
Example 2 Write an equation involving sin, cos, or tan that could be used to find the value of x. Then solve the equation. Round to the nearest tenth. 8 30° x
Example 3 Solve ∆XYZ. Round measures of the sides to the nearest tenth and measures of angles to the nearest degree. X 10 35° z ZxY Find x and y Find Y
Example 4 Solve ∆ABC. Round measures of the sides to the nearest tenth and measures of angles to the nearest degree. B 13 5 C 12 A Find A Use a calculator and the SIN–1 function to find the angle whose sine is 5/13 . Find B
Example 5 In order to construct a bridge across a river, the width of the river at the location must be determined. Suppose a stake is planted on one side of the river directly across from a second stake on the opposite side. At a distance 30 meters to the right of the stake, an angle of 55°, find the width of the river. w 55° 30 m
Elevation and Depression • There are many applications requiring trigonometric solutions. A prime example would be surveyors use of special instruments to find the measures of angles of elevation and angles of depression. • Angle of elevations is the angle between a horizontal line and the line of sight from an observer to an object at a higher level. • Angle of depression is the angle between a horizontal line and the line of sight from the observer to an object at a lower level. • These two are equal measures because they are alternate interior angles.
Example 6 The Aerial run in Snowbird, Utah, has an angle of elevation of 20.2°. It’s vertical drop is 2900 feet. Estimate the length of this run.
Daily Assignment • Chapter 13 Section 1 • Study Guide • Pg 175 – 176 All