已知a=(sinx,cosx),b=(1,-1).1.若=π/2,求x 2.求/a-b/的最大值

问题描述:

已知a=(sinx,cosx),b=(1,-1).1.若=π/2,求x 2.求/a-b/的最大值

1.=π/2,有0=a*b=sinx-cosx=√2*√2/2sinx-√2*√2/2cosx=√2sinxcosπ/4-√2sinπ/4cosx=√2sin(x-π/4)x-π/4=kπ,k是整数x=kπ+π/4,k是整数2.|a-b|^2=(sinx+1)^2+(cosx-1)^2=3+2(sinx-cosx)=3+2√2sin(x-π/4...