Explanation
Question 85
[tex]cos(sec_^{^{-1}}x)[/tex]
so we will have to simplify
[tex]\begin{gathered} let \\ \theta=sec^{-1}x \\ so\text{ that} \\ sec\theta=x \end{gathered}[/tex]
Thus,
[tex]\begin{gathered} \frac{1}{cos\theta}=x \\ cos\theta=\frac{1}{x} \end{gathered}[/tex]
Therefore
The answer for question 85 is 1/x
