In the triangle with angle bisector of meets in . If , find all the angles. (Canada 1996)
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Solution
Since is the bisector of the angle , it follows that , and because of that .
Triangles and have a common angle in vertex and equal ratios of corresponding sides so they are similar. Hence .
Let . Then and . Furthermore, .
Since the triangle is isosceles, we have . As , we get
whence follows . The angles of the observed triangle are and .
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