Question

Attached is the problem, if anyone could help me and explain this I would be grateful.

Answer 1

let's say that, that equals some angle θ
thus
`\bf sec^(-1)(1)=\theta \iff sec(\theta)=1\\\\ -----------------------------\\\\ sec(\theta)=\cfrac{1}{cos(\theta)}\qquad thus\\\\ -----------------------------\\\\ \cfrac{1}{cos(\theta)}=1\implies \cfrac{1}{1}=cos(\theta)\implies 1=cos(\theta) \\\\\\ \textit{now, taking }cos^(-1)\textit{ to both sides} \\\\\\ cos^(-1)(1)=\theta`

so.. .check your Unit Circle, what is that angle anyway?