令f(x) = sin(2x+π/4)
g(x) = cos(2x- 3π/4) = cos(3π/4 - 2x)
= cos[π/2 - (2x - π/4)]
= sin(2x - π/4)
二者的图像关于原点对称,则对任何x,f(x) + g(-x) = 0
f(x) + g(-x)
= sin(2x+π/4) + sin(-2x - π/4)
= sin(2x + π/4) - sin(2x + π/4)
=0
二者的图像关于原点对称