Current location - Training Enrollment Network - Mathematics courses - Nangang district, Harbin, 20 10, with 28 questions in the final math test for Grade Three.
Nangang district, Harbin, 20 10, with 28 questions in the final math test for Grade Three.
1。 It is proved that the sum of these two angles is equal to 180 degrees, so we can know that ADBC is a four-point circle.

Then angle BDC= angle BAC=60 degrees, angle ADC= angle ABC=60 degrees.

Angle ABC= Angle BAC=60 degrees (known)

Therefore, angle ADC= angle BDC, that is, DC bisecting angle ADB.

2。 Under the condition of 1, we know that ABC is a regular triangle, then we know that CF=BE from AF=CE, and then we prove that the triangle ABE and BCF are congruent.

So Angel ·FBC = Angel Pei. . . DH=2, HC=2, root number 3, then CD=2+2, root number 3.