question 8b (v) in SGS trial (1 Viewer)

[mathsbrain]

Question 8 in this paper looks relatively easy, except for 8b(v) which i can't seem to be getting the right answer, i kept getting n< some constant, but clearly n needs to be >some constant. I hope someone can help...

 

[abecina]

I got |cos(theta/2^n)-1| <10^-10

The inequality sign has to switch when you take the inverse cos of both sides, since the function cos x is monotic decreasing when x is increasing on the domain for which the inverse is defined .

Hope that helps