As shown in the figure (10), it is known that ∠C=2∠B in △ABC, and AD divides ∠BAC by d?

Proof: AB=AC+DC.

As shown in the figure, it is known that ∠BAC=∠BCA in △ABC, and AD is the center line of △ABC. Extend BC to f so that CF=AB. ?

Proof: AF=2AD.

As shown in the figure, the diagonal AC and BD of quadrilateral ABCD are compared with point O, △ ABC △ bad.

Verification: (1) OA = ob; (2)AB∑CD

As shown in the figure, ∠ b = ∠ c = 90, m is the midpoint of BC, and DM is divided by ∠ADC. Prove: I am equally divided.

, known: at △ABC, BC= 10,? D is a point on AC, AB=BD,? e，？ F is AD and BC respectively? The midpoint of. Question: the length of EF