sin15度-cos15度=根号2×(根号2)/2×(sin15度-cos15度)=根号2×[sin15度×(根号2)/2-cos15度×(根号2)/2]=根号2×[sin15度×cos45度-cos15度×sin45度]=根号2×sin(15°-45°)=根号2×sin(-30°)=根号2×(-1/2)=-(根...