Question

Cos(2arcsin12/12);

Arccos^2 x-6arccos x+5=0

Answer 1

1)cos(2arccos5/13)=-5/13
2)arccos x=a
a²-6a+5=0
a1+a2=6 U a1+a2=5⇒
a1=1⇒arccos x=1⇒x=0
a2=5⇒arccos x=5⇒нет решения