错
ch²x-sh²x
=(chx+shx)(chx-shx)
={[e^x+e^(-x)]/2+[e^x-e^(-x)]/2}{[e^x+e^(-x)]/2-[e^x-e^(-x)]/2}
=e^x*e^(-x)
=1
所以sh²x+1=ch²x