已知函数F(x)=根号[(1-t)/(1+t)],g(x)=cosx*f(sinx)+sinx*f(cosx)
问题描述:
已知函数F(x)=根号[(1-t)/(1+t)],g(x)=cosx*f(sinx)+sinx*f(cosx)
(1)将函数g(x)化简成Asin(wx+a)+B(A>0,w>0,a∈〔0,2π〕)的形式
(2)求g(x)的值域
a∈【0,2π】 x∈[0,17π/12] f(x)改为f(t)
答
(1) f(t)=√[(1-t)/(1+t)]
f(sinx)=√[(1-sinx)/(1+sinx)]
f(cosx)=√[(1-cosx)/(1+cosx)]
g(x)=cosx*f(sinx)+sinx*f(cosx)
=cosx*√[(1-sinx)/(1+sinx)]+sinx*√[(1-cosx)/(1+cosx)]
=√[((cosx)^2*(1-sinx))/(1+sinx)]+
√[((sinx)^2*(1-cosx))/(1+cosx)]
=√[((1-(sinx)^2)*(1-sinx))/(1+sinx)]+
√[((1-(cosx)^2)*(1-cosx))/(1+cosx)]
=√[((1+sinx)*(1-sinx)*(1-sinx))/(1+sinx)]+
√[((1+cosx)*(1-cosx)*(1-cosx))/(1+cosx)]
=√[(1-sinx)^2]+√[(1-cosx)^2]
=1-sinx+1-cosx
A>0,w>0,a∈【0,2π】
g(x)=2-sinx-cosx
=√2sin(x-3π/4)+2
(2)由-π/2 +2kπ