sin^2 22.5度-cos^2 22.5度=

sin^2 22.5度-cos^2 22.5度=
sin^2 22.5度-cos^2 22.5度=

sin^2 22.5度-cos^2 22.5度=
sin^2 22.5度-cos^2 22.5度= -（cos^2 22.5度-sin^2 22.5度）=-cos45度=-√2/2
45

sin² 22.5°-cos² 22.5°=-cos45°=-0.7071

sin^222.5-(1-sin^222.5)=2sin^222.5-1=-(1-2sin^222.5)=-cos45度=-根2/2