略
(1)画对对称点
.
(2)画对△
(A).
①平行.
理由:∵∠DCE=∠ACE
=∠
=∠
,
∴∠BAC=∠
=∠
.
∴AB∥CD
.
②∵四边形ABCD
是等腰梯形,
∴∠ABC=∠
=2∠BAC=2∠
.
∵AB=AC∴∠ABC=∠ACB=2∠
,
在△ABC中,∠A+∠ABC+∠ACB=180°,
解之得∠
=36°
略
(1)画对对称点
.
(2)画对△
(A).
①平行.
理由:∵∠DCE=∠ACE
=∠
=∠
,
∴∠BAC=∠
=∠
.
∴AB∥CD
.
②∵四边形ABCD
是等腰梯形,
∴∠ABC=∠
=2∠BAC=2∠
.
∵AB=AC∴∠ABC=∠ACB=2∠
,
在△ABC中,∠A+∠ABC+∠ACB=180°,
解之得∠
=36°