Question 206813
altitudes  are  the  same,,,,,,,,,,,,,,,given
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Altitudes  are  perpendicular  to a  side,
therefore resultant  triangles  are  rt  triangles,,,,,,,,def  altitude & def  rt  triangle
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{  2 sketches  might  help,  isosceles  triangles  with altitudes to each equal  side)
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Base  of  the  triangles  are  equal, ,,,,,,,,,,,same  side 
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Triangles  created  by  altitudes and  common base
are  congruent,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,by  HL( hypotenuse  leg)
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Therefore, side  of  each  triangle, bisected  by  the  altitude
are equal, and  base  angles  are  equal,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,by CPCTC 
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Therefore, triangles  are  isosceles,,,,,,,,,,by  def  of  isosceles triangle
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,(2  angles  equal)