8/2.5
= 80/25
= 16/5
= 3 1/5
Using the unit circle, you can visualise the secant as follows:
- Draw the vertical line passing trough (1,0)
- Extend the radius until it meets this line at point P
- The length of OP is the secant of your angle.
Since -90 means that the radius points downwards, it means that the radius is vertical as well, and thus it never meets the vertical line through (1,0).
Thus, the secant is not defined at -90.
In fact, if we switch back to the function notation, we can confirm this claim, since we have

which is undefined.
Based in your question where as ask on which of the following is the equivalent to x^2/xy^2 when y=0 and z=0 and based on my calculation and understanding the possible outcome of your equation will just result to zero but the answer is i think all of them
Let
x---------> the length of the rectangle
y--------> the width of the rectangle
we know that
A=84 ft²
[area of rectangle]=x*y-----> 84=x*y-----> equation 1
x=y-5------> equation 2
substitute 2 in 1
84=[y-5]*y-----> 84=y²-5y---------> y²-5y-84=0
using a graph tool-----> to resolve the second order equation
see the attached figure
the solution is
y=12
x=y-5-----> x=12-5-----> x=7
the answer isthe length of the rectangle is 7 ftthe width of the rectangle is 12 ft