A:arctan 1a
B:﹣arctan 1a
C:π﹣arctan 1a
D:π+arctan 1a
下列有关生态工程的说法错误的是
— So many problems! I'm too tired.
— You should try ________ them by yourself.
证明:∵EF∥AD( )
∴∠2= ( )
又∵∠1=∠2( )
∴∠1=∠3( )
∴AB∥ ( )