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A problem in Trigonometry (Properties of Triangles)

  1. May 11, 2017 #1
    • Member warned that the homework template must be used, and an effort shown
    In any triangle ABC, prove that $$(b+c-a) \left( \cot {\frac {B}{2}} + \cot {\frac {C}{2}} \right)=2a \cot {\frac {A}{2}} $$
  2. jcsd
  3. May 11, 2017 #2
    Did you try to solve this ?
    Also you should not vandalise the template.
  4. May 11, 2017 #3
    I tried in several ways, trying to change a, b, c to 2R sin A and like that, or trying the formulae for cot A/2, but got nowhere.
  5. May 11, 2017 #4
    Use sine rule and A + B + C = 180.
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