Question

What is arccos(cos7)=?

Answer 1

are we using the definition of \(\arccos x\) whose image is \([0,\pi)\)?

Answer 2

yes

Answer 3

in that case recognize \(2\pi\lt7\lt3\pi\) hence \(\arccos(\cos7)=\arccos(\cos(7-2\pi))=7-2\pi\)

Answer 4

3pi-7 too?

Answer 5

i guess 3pi will change the angle?

Answer 6

@oldrin.bataku ?

Answer 7

@DLS \(\cos(3\pi-7)=\cos(2\pi+\pi-7)=\cos(\pi-7)=\cos(7-\pi)\ne\cos(7)\)

Answer 8

okay thanks!