The process of finding unknown elements from known elements except right angles in right triangles is called solving right triangles. As shown in the figure: in Rt ABC, C=90, what is the relationship between the other five elements? C A B b c a returns the solution of right triangle 1 The relationship between two acute angles: 2. Tripartite relationship: 3. The relationship of angles ∠ A+∠ B = 900A2+B2 = C2A C B B B C China = A C COSA = B C Tana = A B Some concepts often encountered in solving right triangle and their applications. (2) slope I = H L concept feedback (1) elevation angle and depression angle sight vertical line horizontal line sight elevation angle depression angle (3) azimuth angle 30 45 b oa, East, west, north, south and A are slope angles = Tan α 24O5.5m A B C Solution: COSA = AC/AB ∴ AB = AC/COSA = 5.5/0.9135 ≈ 6.0 (m) A: The slope distance between two adjacent trees on the slope is 6.0 (plant spacing). Find the slope distance between two adjacent trees on the slope (accurate to 0. 1m). 2. As shown in Figure 7-3-4, there is a slope AB at the entrance of the underground garage, and the slope I = 1. And AB = m. Figure 7-3-4 Warm-up Example C 1 As shown in the figure, there is a slope near the school flagpole. Xiaoming is going to measure the height of school flagpole AB. He found that when the slope is facing the sun, the shadow of flagpole AB just falls on the horizontal ground and the slope of the slope. At this time, the shadow length BC measured by Xiao Ming on the horizontal ground is 20m, the shadow length CD=8 on the slope is 8m, and the sun ray AD is horizontal. (accurate to 1 m) AB D C E Q 20 8 260 4 cases 2 As shown in the figure, there is a slope near the school flagpole. Xiaoming is going to measure the height of school flagpole AB. He found that when the slope is facing the sun, the shadow of flagpole AB just falls on the horizontal ground and the slope of the slope. At this time, the shadow length BC on the horizontal ground measured by Xiao Ming is 20 m, the shadow mark CD=8 on the slope is 8 m, and the sun ray AD is parallel to the horizontal ground.