In a trapezoid ABCD, AB is parallel to CD, angle BCD equals 90 degrees, AB equals 1, BC equals 2, Tan angle ADC equals 2, and E is a point in the trapezoid The angle EDC is equal to the angle FBC and De is equal to BF. Try to judge the shape of triangle ECF and prove your conclusion

In a trapezoid ABCD, AB is parallel to CD, angle BCD equals 90 degrees, AB equals 1, BC equals 2, Tan angle ADC equals 2, and E is a point in the trapezoid The angle EDC is equal to the angle FBC and De is equal to BF. Try to judge the shape of triangle ECF and prove your conclusion

Do am ⊥ CD ∫ ab ∥ CD, ∪ BCD = ∫ ABC = 90 °; ABCM is rectangular ∨ am = BC = 1ab = cm = 1 ∫ Tan ∫ ADC = am / DM ∫ DM = am / Tan ∫ ADC = 2 / 2 = 1 ∫ CD = DM + cm = 1 + 1 = 2 ∫ BC = CD ∫ de = BF ∫ EDC = ≌ FBC ≌ CDE ≌ CBF ∫ CE = CF ∫ BCF = ∫ DCE ∫ DCE + ∫ BCE = 90 °