f(x)=sinx+sinxcosπ/2+sinπ/2cosx=sinx+cosx=√2sin(x+π/2)T=2π/1=2πF(X)的最大值√2 最小值是-√2F(X)=3/4f(x)=sinx+cosx=3/4 ,两边平方得 1+2sinxcosx=9/16 ,所以 sin2x=2sinxcosx=9/16-1=-7/16 ....怎么f(x)=sinx+sinxcosπ/2+sinπ/2cosx=sinx+cosx？？cosπ/2=0sinπ/2=1f(x)=sinx+sinxcosπ/2+sinπ/2cosx=sinx+0*sinx+1*cosx我不明白最大值和最小值从何求来？f(x)=sinx+sinxcosπ/2+sinπ/2cosx =sinx+cosx =√2sin(x+π/2)当x+π/2=π/2+2kπx=2kπ时 取到最大值x+π/2=3π/2+2kπx=π+2kπ时取到最小值sina∈[-1,1]