已知f(x)=?(a的x次方-a的-x次方),g(x)=?(a的x次方+a的-x次方)求证:[f(x)]2+[g(x)]2=g(2x)

问题描述:

已知f(x)=?(a的x次方-a的-x次方),g(x)=?(a的x次方+a的-x次方)
求证:[f(x)]2+[g(x)]2=g(2x)

[f(x)]2+g[(x)]2=[(a)x-(a)(-x)]2+[(a)x+(a)(-x)]2
=[(a)x]2-2*(a)x*(a)(-x)+[(a)(-x)]2+[(a)x]2+2*(a)x*(a)(-x)+[(a)(-x)]2
=2(a)(2x)+2(a)(-2x)=2[(a)(2x)+(a)(-2x)]=2g(2x)