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Section 10.1 Tangent Ratios. For a given acute angle / A with a measure of θ°, the tangent of / A, or tan θ, is the ratio of the length of the leg opposite.

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Presentation on theme: "Section 10.1 Tangent Ratios. For a given acute angle / A with a measure of θ°, the tangent of / A, or tan θ, is the ratio of the length of the leg opposite."— Presentation transcript:

1 Section 10.1 Tangent Ratios

2 For a given acute angle / A with a measure of θ°, the tangent of / A, or tan θ, is the ratio of the length of the leg opposite / A to the length of the leg adjacent to / A in any right triangle having A as one vertex, or tan θ = opposite/adjacent

3 Tangent Ratio Examples Find the tan θ. A D θ θ adj. hyp. hyp. 2.7 adj. 5 B C E F opp. 12opp. 3.6 tan θ = opp./adj. tan θ = 12/5 ≈ 2.4tan θ = 3.6/2.7 ≈ 1.333

4 Finding Angles Using Tangent Ratios Find the indicated angle. X W 12 R T 8 Y P Find / Y.Find / W. tan Y = 6/8tan W = 22.57/12 / Y = tan⁻¹(6/8)/ W = tan⁻¹(22.57/12) / Y = ° / W = 62 °

5 Finding Side Measurements Using Tangent Ratios Find the indicated side. M N B 75 ° x 12 x 37 ° D H G 18 tan 37 = x/18tan 75 = x/12 18tan37 = x12tan75 = x ≈ x44.78 ≈ x

6 Finding Side Measurements Using Tangent Ratios Find the indicated side. M N B 53 ° 5 x ° D H G x tan 42 = 5/xtan 53 = 22/x 5/tan42 = x22/tan53 = x 5.55 ≈ x16.58 ≈ x

7 Section 10.2 Sines and Cosines

8 Sine and Cosine Ratios For a given angle / A with a measure of θ°, the sine of / A, or sin θ, is the ratio of the length of the leg opposite A to the length of the hypotenuse in a right triangle with A as one vertex, or sin θ = opposite/hypotenuse The cosine of / A, or cos θ, is the ratio of the length of the leg adjacent to A to the length of the hypotenuse, or opp. cos θ = adjacent/hypotenuse adj θ° hyp.

9 Sine and Cosine Ratio Examples Find the sin θ and cos θ. A D θ θ adj. hyp. hyp. 2.7 adj. 5 B C E F opp. 12opp. 3.6 sin θ = opp./hyp. cos θ = adj./hyp. sin θ = 12/13 cos θ = 5/13 sin θ = 3.6/4.5 cos θ = 2.7/4.5 sin θ ≈ 0.92 cos θ ≈ 0.38 sin θ ≈ 0.8 cos θ ≈ 0.6

10 Finding Angles Using Sine and Cosine Find the indicated angle. X W 12 R T 8 Y P Find / Y.Find / W. sin Y = 6/10cos Y = 8/10sin W = 22.57/25.56 cos W = 12/25.56 / Y = sin⁻¹(6/10) / Y = cos⁻¹(8/10) / W = sin⁻¹(22.57/25.56) / W = cos⁻¹(12/25.56) / Y ≈ ° / Y ≈ ° / W = 62 ° / W = 62 °

11 Finding Side Measurements Using Tangent Ratios Find the indicated side. M N 45 B 75 ° x ° x D H G sin 34 = x/25cos 75 = x/45 25sin34 = x45cos75 = x ≈ x9.36 ≈ x

12 Two Trigonometric Identities tan θ = sin θ/cos θ (sin θ)² + (cos θ)² = 1

13 Section 10.3 Extending the Trigonometric Ratios

14 Extending Angle Measure Imagine a ray with its endpoint at the origin of a coordinate plane and extending along the positive x-axis. Then imagine the ray rotating a certain number of degrees, say θ, counterclockwise about the origin. θ can be any number of degrees, including numbers greater than 360°. A figure formed by a rotating ray and a stationary reference ray, such as the positive x-axis, is called an angle of rotation.

15 The Unit Circle The unit circle is a circle with its center at the origin and a radius of 1. In the language of transformations, it consists of all the rotation images of the point P(1, 0) about the origin. P(1, 0)


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