The cotangent of a number is given by:
[tex]\begin{gathered} \text{cot(}\theta)\text{ = }\frac{1}{tg(\theta)}=\frac{1}{\frac{sen(\theta)}{\text{cos(}\theta)}} \\ \text{cot(}\theta)\text{ = }\frac{cos(\theta)}{\sin (\theta)} \end{gathered}[/tex]Since the value of the cotangent is undefined, the value of the sine must be equal to 0. Thefore:
[tex]\sin (\theta)=0[/tex]We know that when the sine of an angle is equal to 0, its cosine is equal to 1 or -1. Since the interval is from pi/2 to 3pi/2. Thefore:
[tex]cos(\theta)=-1[/tex]The tangent is the division between the sine and cosine.
[tex]\begin{gathered} \tan (\theta)=\frac{0}{-1} \\ \tan (\theta)=0 \end{gathered}[/tex]The cossec is the inverse of the sine.
[tex]\text{cos}\sec \text{(}\theta)\text{ = }\frac{1}{\sin (\theta)}=\frac{1}{0}\text{ = undefined}[/tex]The sec is the inverse of the cossine.
[tex]\text{sec(}\theta)=\frac{1}{\text{cos(}\theta)}=\frac{1}{-1}=-1[/tex]