已知f(cosx/2)=3cosx+2,则f(sinπ8)= _ .
问题描述:
已知f(cos
)=3cosx+2,则f(sinx 2
)= ___ . π 8
答
=t,则cosx=2cos2
-1=2t2-1,
∴f(t)=6t2-1,
∴f(sin
)=6sin2
-1=6×
-1=3-
-1=2-
.
故答案为:2-
设cos
x |
2 |
x |
2 |
∴f(t)=6t2-1,
∴f(sin
π |
8 |
π |
8 |
1−cos
| ||
2 |
3
| ||
2 |
3
| ||
2 |
故答案为:2-
3
| ||
2 |