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Warm_Up 5 1. The pilot of a small plane is flying at an altitude of 2000 ft. The pilot plans to start the final descent toward a runway when the horizontal distance between the plane and the runway is 2 mi. To the nearest degree, what will be the angle of depression θ from the plane to the runway at this point? 2. cos θ = 0.3, for 3π/2 < θ < 2π 13.5 Law of Sines
Law of Sines Section 13.5 13.5 Law of Sines
Use of Law of Sines • Two angle measures and any side length–angle-angle-side (AAS) or angle-side-angle (ASA) information • Two side lengths and the measure of an angle that is not between them–side-side-angle (SSA) information • Allows for triangles to find the missing side or angle • Law of Cosines are primarily used for SSS and SAS triangles 13.5 Law of Sines
Equation • Put the equation as a proportion • Cross Multiply • Solve for the missing angle or side • Side always associates itself with OPPOSITE • Triangle has 180 degrees • Can’t use SOHCAHTOA because there is not a 90 degree angle Note: Letters A, B, C are not always going to be used as ‘A,’ ‘B,’ or ‘C’ 13.5 Law of Sines
sin F sin D = d f sin 28° sin 33° = d 15 15 sin 33° d = sin 28° Example 1 Solve for d. Law of Sines. Substitute. d sin 28° = 15 sin 33° Cross multiply. Solve for the unknown side. d ≈ 17.4017 13.5 Law of Sines
r Q Your Turn Determine q and r. 13.5 Law of Sines
C C b 20 a 50 A B B c c Example 2 Determine the number of triangular banners that can be formed using the measurements a = 50, b = 20, and mA = 28°. Then solve for mB, mC, and side C. Round to the nearest tenth. 13.5 Law of Sines
C 20 50 B c Example 2 Determine the number of triangular banners that can be formed using the measurements a = 50, b = 20, and mA = 28°. Then solve for mB, mC, and side C. Round to the nearest tenth. Law of Sines Substitute. Solve for sin B. C = 141.2°, c = 66.7 13.5 Law of Sines
Your Turn Determine the number of triangular quilt pieces that can be formed by using the measurements a = 14 cm, b = 20 cm, and A = 39°. Solve for the missing sides. c1 21.7 cm; mB1≈ 64.0°; mC1≈ 77.0°; 13.5 Law of Sines
Example 3 Given the points of (5, 3), determine the angle measure. 3 5 13.5 Law of Sines
Your Turn Given the points of (–4, 3), determine the angle measure. 13.5 Law of Sines
Page 962 13.5 Law of Sines
Review Pg 978 39-47, 49, 51, 57-61 13.5 Law of Sines
Assignment Page 962 5-9 odd, 17, 19, 24, 29 13.5 Law of Sines