Представьте в виде произведения: сos \(\frac{\Pi}{5}\) + cos \(\frac{\Pi}{4}\) .​

• 2 \(\cdot\) cos \(\frac{9\Pi }{40}\) \(\cdot\)
  cos \(\frac{\Pi}{40}\) ​
• 2 \(\cdot\) cos \(\frac{\Pi}{20}\) \(\cdot\)
  cos \(\frac{9\Pi }{20}\) ​