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在人教版数学七年级下册第七章《三角形》中有这样一道例题,其题目和解答如下:例题:如图(即图1),C岛在A岛的北偏东50°方向,B岛在A岛的北偏东80°方向,C岛在B岛的北偏西40°方向。从C岛看A、B两岛的视角∠ACB是多少度?
In the PEP Teaching in the seventh grade “Triangle” there is such a case, the title and answer are as follows: Example: As shown in Figure 1, C Island in A Island north east 50 ° direction, Island B is 80 ° to the east of island A and 40 ° north to west of island B. From C Island to see A, B two island perspective? ACB is how many degrees?