(1)tanα=
=sinα cosα
,α∈(3 4
,π 2
),3π 2
sin2α+cos2α=1
所以sinα=?
,3 5
cosα=-
4 5
∴
=sin(π+α)?sin(
+α)3π 2 cos(3π?α)+2
=?sinα+cosα ?cosα+2
=?
?3 5
4 5
+24 5
;1 14
(2)sin(-
-α)=-(π 4
cosα+
2
2
sinα)=
2
2
.7
2
10