Вычислите.

• Объекты 1
  • \(\sin{\frac{9\pi}{7}}\cos{\frac{2\pi}{7}}-\cos{\frac{9\pi}{7}}\sin{\frac{2\pi}{7}}\)
  • \(\cos{\frac{7\pi}{12}}\cos{\frac{5\pi}{12}}+\sin{\frac{7\pi}{12}}\sin{\frac{5\pi}{12}}\)
  • \(\sin{12^\circ}\cos{78^\circ}+\cos{12^\circ}\sin{78^\circ}\)
  • \(\sin{21^\circ}\sin{24^\circ}-\cos{21^\circ}\cos{24^\circ}\)
• Объекты 2
  • \(\frac{1}{2}\)
  • \(-\frac{\sqrt{2}}{2}\)
  • \(0\)
  • \(\frac{\sqrt{3}}{2}\)
  • \(1\)
  • \(-1\)