问题
选择题
已知cosα=
|
答案
∵cosα=
，2 3
∴cos（π+2α）=-cos2α=-（2cos2α-1）=-2×(
)2+1=2 3
．1 9
故选C
搜题请搜索小程序“爱下问搜题”
已知cosα=
|
∵cosα=
，2 3
∴cos（π+2α）=-cos2α=-（2cos2α-1）=-2×(
)2+1=2 3
．1 9
故选C
| 32．Communicating via E-mail is by far the most common Internet activity. You can (1) with anyone in the world who has an Internet address or E-mail (2) with a system connection to the Internet. All you need is (3) the Internet and an E-mail program Two of the most widely used E-mail programs are Microsoft’s (4) and Netscape’s Navigator. A typical E-mail message has three basic (5) ：header, message, and signature. |
(3)
A．attach with
B．grasp
C．possess
D．access to