Упростите выражение а cos2 a-cos4 a+sin4 a

cos(2)a-cos(4)a+sin(4)a=cos(2)a(1-cos(2)a)+sin(4)a=cos(2)a*sin(2)a+sin(4)a
(sin(2)a=1-cos(2)a)=
=sin(2)a(cos(2)a+sin(2)a)=
(sin(2)a+cos(2)a=1)
=sin(2)a