已知向量a=(根號(hào)3,1),向量b=(sin3x/2,cos3x/2).函數(shù)f(x)=向量a乘以向量b+m,恒過點(diǎn)(-π/3,1)
已知向量a=(根號(hào)3,1),向量b=(sin3x/2,cos3x/2).函數(shù)f(x)=向量a乘以向量b+m,恒過點(diǎn)(-π/3,1)
(1)求m的值
(2)求函數(shù)y=f(x)的最小正周期及單調(diào)遞減區(qū)間
優(yōu)質(zhì)解答
(1)f(x)=a*b=(根號(hào)3倍的sin3x/2)+(cos3x/2)+m=2cos(3x/2-π/3)+m
代(-π/3,1)得f(-π/3)=2cos(-5π/6)+m=1則m=根號(hào)3+1
(2)由(1)知T=2π/w=4π/3
且2kπ=<3x/2-π/3=<2kπ+π(k屬于Z)時(shí)單減,整理得4π/3+3π/9=