train
A:station
B:bus
如图,已知四边形ABCD内接于圆,对角线AC与BD相交于点E,F在AC上,AB=AD,∠BFC=∠BAD=2∠DFC.
(1)若∠DFC=40°,求∠CBF的度数;
(2)求证:CD⊥DF.
You _____ tell anybody about this— —it's a secret.
【操作】将三角板DEF的直角顶点E放置于三角板ABC的斜边AC上,再将三角板DEF绕点E旋转,并使边DE与边AB交于点P,边EF与边BC于点Q
自习课上,当同学们都在认真学习的时候,张晓钢抬起头来,想跟别人说与学习无关的话。从个人与集体的关系角度,你应该告诉他( )