Section 5.6 The Law of Sines Objective: Students will be able to: 1.Solve triangles using the Law of Sines if the measures of 2 angles and a side are given. 2.Find the area of a triangle if the measures of 2 sides and the included angle or the measures of 2 angles and a side are given.
Law of Sines
Example 1: Solve ABC if A = 24°, B = 62°, and a = First, find the measure of C. C = 180° - (24° + 62°) or 94° Use the Law of Sines to find b and c b c
Example 2: The angle of depression from a window of a house to the front edge of the swimming pool is 26.6°. The angle of depression from this same window to the back edge of the swimming pool is 15.3°. The length of the pool is 25 feet. If a person looks out the window, about how far is he from the front edge of the pool? *** Make a diagram of the problem. Remember that the angle of elevation is congruent to the angle of depression because they are alternate interior angles. First, find . = 26.6° ° or 11.3° Use the Law of Sines to find d. d The person would be about 33.7 feet from the front edge of the pool.
Example 3: Find the area of ABC if b = 14.8, c = 10.2, and A = 54°12. K The area of ABC is about 61.2 square units.
Example 4: Find the area of DEF if e = 18.6, E = 78.2°, and F = 41.3°. First find the measure of D. D = 180° - (78.2° °) or 60.5° Then, find the area of the triangle. K The area of DEF is about square units.