China Naming Network - Weather knowledge - (20 12? As shown in the figure, in △ABC, AD is the center line of BC, BC=4, ∠ ADC = 30, and △ADC folds back to point C along the straight line where AD is located.
(20 12? As shown in the figure, in △ABC, AD is the center line of BC, BC=4, ∠ ADC = 30, and △ADC folds back to point C along the straight line where AD is located.
Answer: DE⊥BC' in E.
According to the nature of folding, CD = c'd, ∠ADC'=∠ADC = 30.
∵AD is the center line of triangle ABC,
∴BD=CD=2，
∴bd=c′d=2.
DE⊥BC'，
∴∠bde=∠c′de=60。
∴de= 12c′d= 1.