In trapezoidal ABCD, AD / / BC, ab = CD = 2, BC = 6, point E is on BD, and angle DCE = angle ADB 1) Find out all the similar triangles in the graph and prove them; 2) Let BD = x, be = y, find the analytic expression of Y with respect to x, and write out its domain of definition; 3) When ad = 4, find the length of be

In trapezoidal ABCD, AD / / BC, ab = CD = 2, BC = 6, point E is on BD, and angle DCE = angle ADB 1) Find out all the similar triangles in the graph and prove them; 2) Let BD = x, be = y, find the analytic expression of Y with respect to x, and write out its domain of definition; 3) When ad = 4, find the length of be

1) Because AD / / BC, angle ADB = angle DBC, because AB = CD, AD / / BC, angle DCE = angle, ADB = angle DBC, so angle abd = angle ECB, so triangle abd is similar to triangle ECB, because angle DCE = angle DBC, angle EDC and angle CDB are the same angle, so triangle EDC is similar to triangle cdb2