Question

I don't understand how cos(110) deg= -cos(30)deg.

What does -cos even mean??
I was given a formula cos x= -cos(180-x) which I don't fully understand either.

Answer 1

\(\Large \color{MidnightBlue}{\Rightarrow cos = {adjacent \over hypotenuse} }\)

Answer 2

I understand what cosine is but what does the negative sign do to it??

Answer 3

@lalaly @Mertsj

Answer 4

cos (60) for example=1/2
cos (180-60)=cos(120) =-1/2