问题
填空题
在△ABC中,若cosA=-
|
答案
在△ABC中,∵cosA=-
,∴A为钝角,∴sin5 13
>0.A 2
由二倍角公式可得 cosA=-
=1-2sin25 13
,解得sinA 2
=A 2
,3 13 13
故答案为:
.3 13 13
在△ABC中,若cosA=-
|
在△ABC中,∵cosA=-
,∴A为钝角,∴sin5 13
>0.A 2
由二倍角公式可得 cosA=-
=1-2sin25 13
,解得sinA 2
=A 2
,3 13 13
故答案为:
.3 13 13
用方框中所给单词的适当形式填空,每空限填一词。
小题2:Jenny ________ to be a volunteer (志愿者) in a small village. 小题3:—Are the Smiths ________? —No, they are all American. 小题4:The students will ________ the class monitor when he appears (出现). 小题5:Alice is a nice girl. She often helps her parents with the ________. |