定理证明:“等腰梯形的两条对角线相等”.
证明:在梯形ABCD中,
∵AB=DC,
∴∠ABC=∠DCB.
又∵BC=CB,
∴△ABC≌△DCB.
∴AC=DB.
化简5a2-[a2-2(a2-3a)]的结果是( )
A.6a2-6a
B.6a2+3a
C.6a2+6a
D.4a2-3a
如果你晚上早些睡,早上就不会感觉疲惫。
You go to bed earlier at night, you won’t in the morning.