①sinα=sinβ  ②sinα=-sinβ  ③cosα=cosβ  ④cosα=-cosβ

A.1                   B.2                    C.3                  D.4

A.1+                 B.1-               C.-1-             D.-1+

=-1.

(1);

(2).

(1)sin315°sin(-1 260°)+cos570°sin(-840°);

(2)已知tan(π+α)=3,求

的值.

(1)求f()的值;

(2)设α∈(0,π),f()=-,求sinα的值.