Can someone please help with this❤️❤️❤️

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

Plz me i need i will give a brain

Jack has a piece of red ribbon that is two times as long as his piece of blue ribbon. he says that he can use two different equation to find out how long his piece of red ribbon is compared to his piece of blue ribbon is. is he correct? explain his reasoning