$cos(\underbrace{arccosx}+\underbrace{arcsinx})$
a b
$cos(a+b)=cosa.cosb-sina.sinb$
$arccosx=a \Longrightarrow cosa=x$
$arcsinx=b \Longrightarrow sinb=x$
bu üçgenleri kullanarak ;
$cos(a+b)=cosa.cosb-sina.sinb$ bunu yazalım
$cos(a+b)=x.\frac{\sqrt{1-x^2}}{1}+\frac{\sqrt{1-x^2}}{1}.x=0$
yani
$cos(arccosx+arcsinx)=cos(a+b)=0$ $\Box$