(cos(4次方）派/8）-(sin(4次方）派/8)等于多少?

(cos(4次方）派/8）-(sin(4次方）派/8)等于多少?
(cos(4次方）派/8）-(sin(4次方）派/8)等于多少?

(cos(4次方）派/8）-(sin(4次方）派/8)等于多少?
(cosπ/8)^4-(sinπ/8)^4
=[(cosπ/8)^2+(sinπ/8)^2]*[(cosπ/8)^2-(sinπ/8)^2]
=1*cos（π/4）
=2分之根号2

(cosπ/8)^4-(sinπ/8)^4
=[(cosπ/8)^2+(sinπ/8)^2][(cosπ/8)^2-(sinπ/8)^2]
=1×cos(2×π/8)
=cosπ/4
=√2/2