Question

如图,在三角形ABC中,点D,E在AB上,∠ACB=100度,∠ACE=∠AEC,∠BCD=∠BDC,求

Answer 1

设∠ACE=∠AEC=α,∠BCD=∠BDC=β,

∠BCE=100°-α,

∠B=180°-2β,

∠AEC=∠B+∠BCE,

α=180°-2β+100°-α

α+β=140°,

∠DCE=180°-(∠BDC+∠AEC),

=180°-(β+α),

=180°-140°,

=40°.