设α为锐角,若 cos(α+ π 6 )= 4 5 ,则sinα的值为______

设α为锐角,若 cos(α+ π 6 )= 4 5 ,则sinα的值为______.
2025-02-02 22:38:55
推荐回答(1个)
回答1:

sinα=sin[ (α+
π
6
)
-
π
6
]
∵α为锐角, cos(α+
π
6
)=
4
5
,则sin[ (α+
π
6
)
=
1-(
4
5
) 2
=
3
5

sinα=sin[ (α+
π
6
)
-
π
6
]=sin[ (α+
π
6
)
cos
π
6
-cos (α+
π
6
)
sin
π
6

=
3
5
×
3
2
-
4
5
×
1
2

=
3
3
-4
10

故答案为:
3
3
-4
10