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Prove that,in an isosceles triangle,the bisector of the vertical angle,the altitude from the vertex and the median to the base are coincident. |
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Answer» Answer: Proof: Consider the two triangles ABD and ACD, AB = AC (Given) Angle BAD = Angle CAD (since given AD bisects angle BAC) AD = AD (Common sides) Thus the two triangles ABD and ACD are consistent (By 'SAS' compatibility adage of triangles) therefore angle ADB = edge ADC - (1) (Corresponding parts of CONGRUENCE triangles are equivalent) In any case, these two are direct PAIR that is their entirety is 180 degrees - (2) Thus from (1) and (2), EVERY one of the points ADB and ADC are 90 degrees. Therefore, AD is perpendicular to BC.
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