Bisectors of angles A, B and C of a triangle ABC intersect its circum circle at D, E and F respectively. Prove that the angles of the triangle DEF are  and
 and 
It is given in the question that,
∠ABE = 
However,
 = ∠ADE
 = ∠ADE
Like this, similarly
∠ACF = ∠ADF = 
D = ∠ADE + ∠ADF
=  +
 + 
=  (∠B + ∠C)
 (∠B + ∠C)
=  (180o – ∠A)
 (180o – ∠A)
= 90o -  ∠A
 ∠A
Similarly,
E = 90o -  ∠B
 ∠B
And,
F = 90o -  ∠C
 ∠C