已知sin(π3+α)=3/5,则cos(5π6+α)值为_.
问题描述:
已知sin(
+α)=π 3
,则cos(3 5
+α)值为______. 5π 6
答
∵sin(
+α)=sin[π 3
-(π 2
-α)]=cos(π 6
-α)=π 6
,3 5
∴cos(
+α)=cos[π-(5π 6
-α)]=-cos(π 6
-α)=-π 6
.3 5
故答案为:-
3 5