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Mathematics 3. Angle Bisector theorem. In a triangle the angle bisector divides the opposite side in the ratio of the remaining sides. This means that for a D ABC ( figure 5.5) the bisector of Ð A divides BC in the ratio . To prove that
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Mathematics 3 Angle Bisector theorem
In a triangle the angle bisector divides the opposite side in the ratio of the remaining sides. This means that for a D ABC ( figure 5.5) the bisector of Ð A divides BC in the ratio .
To prove that Through C draw a line parallel to seg.AD and extend seg.BA to meet it at E. seg.CEççseg.DA Ð BAD @ Ð AEC , corresponding angles Ð DAC @ Ð ACE , alternate angles But Ð BAD = Ð DAC , given \ Ð AEC @ Ð ACE Hence D AEC is an isosceles triangle. \ seg.AC @ seg.AE In D BCE AD çç CE Thus the bisector divides the opposite side in the ratio of the remaining two sides.