Zgjidhja e ushtrimit 8

Gjeni vlerën numerike të shprehjeve:

1. cos15$\degree$cos75$\degree$ - sin15$\degree$sin75$\degree$
2. sin135$\degree$cos45$\degree$ + cos135$\degree$sin45$\degree$
3. sin67$\degree$cos22$\degree$ - cos67$\degree$sin22$\degree$
4. cos81$\degree$cos21$\degree$ + sin81$\degree$sin21$\degree$