Restriction Of Parametric Functions Domain The problem I am working on is, "Sketch the curve repres

Kolten Conrad

Kolten Conrad

Answered question

2022-07-01

Restriction Of Parametric Functions Domain
The problem I am working on is, "Sketch the curve represented by the parametric equations (indicate the orientation of the curve), and write the corresponding rectangular equation by eliminating the parameter."
x = sec θ  and  y = cos θ
In the answer key, 0 θ < π / 2 and π / 2 < θ π. What about the angle on the unit circle that are in the third and fourth quadrant?
Also, in the answer key, | x | 1 and | y | 1. Why are x and y restricted in such a way?

Answer & Explanation

Sariah Glover

Sariah Glover

Beginner2022-07-02Added 16 answers

Step 1
It's the curve y = 1 / x restricted to those values of y that can be cos theta, or equivalently, those values of x that can be sec theta.
Remember that 1 cos θ 1, and sec θ is always either 1 or 1.
Step 2
As θ goes from 0 to π, cos θ goes all the way from 1 down to -1. If we went beyond π, we'd see it going through the same set of values again, from -1 back up to +1. We would not get any new values of x or y that we didn't get the first time.

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