# ALEX Classroom Resource

## Geometry Module 2, Topic E: Trigonometry

Classroom Resource Information

Title:

Geometry Module 2, Topic E: Trigonometry

URL:

https://www.engageny.org/resource/geometry-module-2-topic-e-overview

Content Source:

EngageNY
Type: Lesson/Unit Plan

Overview:

Students begin the study of trigonometry in the final topic of the module. The emphasis in the module on side length relationships within similar triangles (Topic C) and the specific emphasis on right triangles
(Topic D) help set the foundation for trigonometry. Lesson 25 is the last highlight of the side length ratios within and between right triangles. Students are guided to the idea that the values of the ratios depend solely on a given acute angle in the right triangle before the basic trigonometric ratios are explicitly defined in Lesson 26 (G.SRT.C.6). After practice with ratios labeled as (Lesson 21) and (Lesson 25), students are introduced to the trigonometric ratios sine, cosine, and tangent (G-SRT.C.6) in Lesson 26. Students examine the relationship between sine and cosine in Lesson 27, discovering that the sine and cosine of complementary angles are equal (G-SRT.C.7). They are also introduced to the common sine and cosine values of angle measures frequently seen in trigonometry. Students apply the trigonometric ratios to solve for unknown lengths in Lessons 28 and 29; students also learn about the relationship between tangent and slope in Lesson 29 (G-SRT.C.8). In Lesson 30, students use the Pythagorean theorem to prove the identity and also show why. In Lessons 3133, students study the application of trigonometry to determine area and solve for unknown lengths using the laws of sines and cosines (G-SRT.9, G-SRT.10, G-SRT.11). Finally, in Lesson 34, students learn how to determine the unknown measure of an angle of a right triangle. Students are introduced to the trigonometric functions and These inverse functions are taught formally in Algebra II. For now, students should understand the meaning of and how to use and to determine unknown measures of angles.

Content Standard(s):
 Mathematics MA2015 (2016) Grade: 9-12 Geometry 20 ) Explain and use the relationship between the sine and cosine of complementary angles. [G-SRT7] Mathematics MA2015 (2016) Grade: 9-12 Geometry 21 ) Use trigonometric ratios and the Pythagorean Theorem to solve right triangles in applied problems.* [G-SRT8] Mathematics MA2019 (2019) Grade: 9-12 Geometry with Data Analysis 35. Discover and apply relationships in similar right triangles. a. Derive and apply the constant ratios of the sides in special right triangles (45o-45o-90o and 30o-60o-90o). b. Use similarity to explore and define basic trigonometric ratios, including sine ratio, cosine ratio, and tangent ratio. c. Explain and use the relationship between the sine and cosine of complementary angles. d. Demonstrate the converse of the Pythagorean Theorem. e. Use trigonometric ratios and the Pythagorean Theorem to solve right triangles in applied problems, including finding areas of regular polygons. Unpacked Content Evidence Of Student Attainment:Students: Given a collection of right triangles, discover and apply relationships in similar right triangles. Derive and apply the ratios of the sides of the original triangles to the ratios of the sides of the similar triangles. Communicate observations made about changes (or no change) to such ratios as the length of the side opposite an angle to the hypotenuse, or the side opposite the angle to the side adjacent, as the size of the angle changes or in the case of similar triangles, remains the same. Summarize these observations by defining the six trigonometric ratios. Explain why the two smallest angles must be complements. Compare the side ratios of opposite/hypotenuse and adjacent/hypotenuse for each of these angles and discuss conclusions. Given a contextual situation involving right triangles, Create a drawing to model the situation. Find the missing sides and/or angles using trigonometric ratios. Find the missing sides using the Pythagorean Theorem. Use the above information to interpret results in the context of the situation, including finding the areas of regular polygons.Teacher Vocabulary:Side ratios Trigonometric ratios Sine Cosine Tangent Secant Cosecant Cotangent Complementary angles converseKnowledge:Students know: Techniques to construct similar triangles. Properties of similar triangles. Methods for finding sine and cosine ratios in a right triangle (e.g., use of triangle properties: similarity. Pythagorean Theorem. isosceles and equilateral characteristics for 45-45-90 and 30-60-90 triangles and technology for others). Methods of using the trigonometric ratios to solve for sides or angles in a right triangle. The Pythagorean Theorem and its use in solving for unknown parts of a right triangle.Skills:Students are able to: Accurately find the side ratios of triangles. Explain and justify relationships between the side ratios of a right triangle and the angles of a right triangle.Understanding:Students understand that: The ratios of the sides of right triangles are dependent on the size of the angles of the triangle. The sine of an angle is equal to the cosine of the complement of the angle. Switching between using a given angle or its complement and between sine or cosine ratios may be used when solving contextual problems.Diverse Learning Needs: Essential Skills:Learning Objectives: GEO.35.1: Define trigonometric (sine, cosine and tangent) ratios for acute angles, complementary angles, and Pythagorean Theorem. GEO.35.2: Simplify, multiply, and divide radicals. GEO.35.3:Discuss the relationship between sine and cosine angles within a triangle. GEO.35.4: Solve equations using trigonometric ratios. GEO.35.5: Apply properties of similarity to demonstrate the trigonometric ratios of right triangles. GEO.35.6: Use Pythagorean Theorem to find the missing side of a right triangle. GEO.35.7: Create an equation using the given information of a right triangle. GEO.35.8: Identify the parts of a right triangle. Examples: legs, hypotenuse, right angle. Prior Knowledge Skills:Demonstrate how to find square roots. Identify right triangles. Solve problems using the Pythagorean Theorem. Recognize ordered pairs (x, y). Recall how to name points on a Cartesian plane using ordered pairs. Identify right triangles. Solve problems using the Pythagorean Theorem. Discuss strategies for solving real-world and mathematical problems. Recognize examples of right triangles. Define a right angle, Pythagorean Theorem, converse, and proof. Apply properties to find missing angle measures. Identify a transversal. Identify exterior, interior, vertical, adjacent, alternate interior, alternate exterior, and corresponding angles. Identify attributes of triangles. Define exterior, interior, vertical, adjacent, alternate interior, alternate exterior, corresponding, and transversal angles. Identify right and straight angles. Identify all types of angles. Identify proportional relationships. Locate/use scale on a map. Define scale, scale drawings, length, area, and geometric figures. Recall how to find unit rates using ratios. Define unit rate, proportions, area, length, and ratio. Analyze the area of other triangles, special quadrilaterals, and polygons by composing into rectangles or decomposing into triangles and other shapes. Define area, special quadrilaterals, right triangles, and polygons. Recognize and demonstrate that two right triangles make a rectangle. Select manipulatives to demonstrate how to compose and decompose triangles and other shapes. Explain how to find the area for rectangles. Demonstrate how the area of a rectangle is equal to the sum of the area of two equal right triangles. Apply area formulas to solve real-world mathematical problems. Recognize polygons. Restate real-world problems or mathematical problems. Calculate unit rate or rate by using ratios or proportions. Create a ratio or proportion from a given word problem, diagram, table, or equation. Define ratio, rate, proportion, percent, equivalent, input, output, ordered pairs, diagram, unit rate, and table. Form a ratio. Solve a proportion using part over whole equals percent over 100. Identify a proportion from given information. Calculate a proportion for missing information. Create a proportion or ratio from a given word problem. Alabama Alternate Achievement Standards AAS Standard: M.G.AAS.10.36 Use geometric shapes to describe real-world objects.
Tags: acute angles, complementary angles, cosine, geometry, Pythagorean Thereom, right triangles, side ratios, similarity, sine, trigonometry