Applying Special Right Triangles Warm Up Lesson Presentation

Applying. Special. Right. Triangles Warm Up Lesson Presentation Lesson Quiz Holt. Mc. Dougal Geometry Holt

Applying Special Right Triangles Warm Up For Exercises 1 and 2, find the value of x. Give your answer in simplest radical form. 1. 2. Simplify each expression. 3. Holt Mc. Dougal Geometry 4.

Applying Special Right Triangles Objectives Justify and apply properties of 45°-90° triangles. Justify and apply properties of 30°- 60°- 90° triangles. Holt Mc. Dougal Geometry

Applying Special Right Triangles A diagonal of a square divides it into two congruent isosceles right triangles. Since the base angles of an isosceles triangle are congruent, the measure of each acute angle is 45°. So another name for an isosceles right triangle is a 45°-90° triangle. A 45°-90° triangle is one type of special right triangle. You can use the Pythagorean Theorem to find a relationship among the side lengths of a 45°-90° triangle. Holt Mc. Dougal Geometry

Applying Special Right Triangles Holt Mc. Dougal Geometry

Applying Special Right Triangles Example 1 A: Finding Side Lengths in a 45°- 45º- 90º Triangle Find the value of x. Give your answer in simplest radical form. By the Triangle Sum Theorem, the measure of the third angle in the triangle is 45°. So it is a 45°-45° 90° triangle with a leg length of 8. Holt Mc. Dougal Geometry

Applying Special Right Triangles Example 1 B: Finding Side Lengths in a 45º- 90º Triangle Find the value of x. Give your answer in simplest radical form. The triangle is an isosceles right triangle, which is a 45°-90° triangle. The length of the hypotenuse is 5. Rationalize the denominator. Holt Mc. Dougal Geometry

Applying Special Right Triangles Check It Out! Example 1 a Find the value of x. Give your answer in simplest radical form. By the Triangle Sum Theorem, the measure of the third angle in the triangle is 45°. So it is a 45°-45° 90° triangle with a leg length of x = 20 Holt Mc. Dougal Geometry Simplify.

Applying Special Right Triangles Check It Out! Example 1 b Find the value of x. Give your answer in simplest radical form. The triangle is an isosceles right triangle, which is a 45°-90° triangle. The length of the hypotenuse is 16. Rationalize the denominator. Holt Mc. Dougal Geometry

Applying Special Right Triangles Example 2: Craft Application Jana is cutting a square of material for a tablecloth. The table’s diagonal is 36 inches. She wants the diagonal of the tablecloth to be an extra 10 inches so it will hang over the edges of the table. What size square should Jana cut to make the tablecloth? Round to the nearest inch. Jana needs a 45°-90° triangle with a hypotenuse of 36 + 10 = 46 inches. Holt Mc. Dougal Geometry

Applying Special Right Triangles Check It Out! Example 2 What if. . . ? Tessa’s other dog is wearing a square bandana with a side length of 42 cm. What would you expect the circumference of the other dog’s neck to be? Round to the nearest centimeter. Tessa needs a 45°-90° triangle with a hypotenuse of 42 cm. Holt Mc. Dougal Geometry

Applying Special Right Triangles A 30°-60°-90° triangle is another special right triangle. You can use an equilateral triangle to find a relationship between its side lengths. Holt Mc. Dougal Geometry

Applying Special Right Triangles Example 3 A: Finding Side Lengths in a 30º-60º-90º Triangle Find the values of x and y. Give your answers in simplest radical form. 22 = 2 x Hypotenuse = 2(shorter leg) 11 = x Divide both sides by 2. Substitute 11 for x. Holt Mc. Dougal Geometry

Applying Special Right Triangles Example 3 B: Finding Side Lengths in a 30º-60º-90º Triangle Find the values of x and y. Give your answers in simplest radical form. Rationalize the denominator. y = 2 x Hypotenuse = 2(shorter leg). Simplify. Holt Mc. Dougal Geometry

Applying Special Right Triangles Check It Out! Example 3 a Find the values of x and y. Give your answers in simplest radical form. Hypotenuse = 2(shorter leg) Divide both sides by 2. y = 27 Holt Mc. Dougal Geometry Substitute for x.

Applying Special Right Triangles Check It Out! Example 3 b Find the values of x and y. Give your answers in simplest radical form. y = 2(5) y = 10 Simplify. Holt Mc. Dougal Geometry

Applying Special Right Triangles Check It Out! Example 3 c Find the values of x and y. Give your answers in simplest radical form. 24 = 2 x Hypotenuse = 2(shorter leg) 12 = x Divide both sides by 2. Substitute 12 for x. Holt Mc. Dougal Geometry

Applying Special Right Triangles Check It Out! Example 3 d Find the values of x and y. Give your answers in simplest radical form. Rationalize the denominator. x = 2 y Hypotenuse = 2(shorter leg) Simplify. Holt Mc. Dougal Geometry

Applying Special Right Triangles Example 4: Using the 30º-60º-90º Triangle Theorem An ornamental pin is in the shape of an equilateral triangle. The length of each side is 6 centimeters. Josh will attach the fastener to the back along AB. Will the fastener fit if it is 4 centimeters long? Step 1 The equilateral triangle is divided into two 30°-60°-90° triangles. The height of the triangle is the length of the longer leg. Holt Mc. Dougal Geometry

Applying Special Right Triangles Example 4 Continued Step 2 Find the length x of the shorter leg. 6 = 2 x 3=x Hypotenuse = 2(shorter leg) Divide both sides by 2. Step 3 Find the length h of the longer leg. The pin is approximately 5. 2 centimeters high. So the fastener will fit. Holt Mc. Dougal Geometry

Applying Special Right Triangles Check It Out! Example 4 What if…? A manufacturer wants to make a larger clock with a height of 30 centimeters. What is the length of each side of the frame? Round to the nearest tenth. Step 1 The equilateral triangle is divided into two 30º-60º-90º triangles. The height of the triangle is the length of the longer leg. Holt Mc. Dougal Geometry

Applying Special Right Triangles Check It Out! Example 4 Continued Step 2 Find the length x of the shorter leg. Rationalize the denominator. Step 3 Find the length y of the longer leg. y = 2 x Hypotenuse = 2(shorter leg) Simplify. Each side is approximately 34. 6 cm. Holt Mc. Dougal Geometry

Applying Special Right Triangles Lesson Quiz: Part I Find the values of the variables. Give your answers in simplest radical form. 1. 2. x = 10; y = 20 3. Holt Mc. Dougal Geometry 4.

Applying Special Right Triangles Lesson Quiz: Part II Find the perimeter and area of each figure. Give your answers in simplest radical form. 5. a square with diagonal length 20 cm 6. an equilateral triangle with height 24 in. Holt Mc. Dougal Geometry