# Parametric equations

1. Sep 18, 2007

### teffy3001

i have a couple questions that confuse me that would help me on doing my homework on parametric equations....

do the parametric equations x=t^2 and y=t^2 describe the line y=x?
and if y is a function of t and x is a function of t, then is y a funcion of x?
and last, does x=cos t, y=cos^2(t) describe the parabola y=x^2?

these arent my homework questions, but any help or explanation of this would really help me out...thanks : )

2. Sep 18, 2007

### symbolipoint

The first question: Yes;
the second question: No.

The cosine function restricts what values x and y can be. Cosine can only be between -1 and +1.

You want to represent your y function as (cos(t))^2 unless you know how to use proper typesetting, such as TEX or something.,

3. Sep 18, 2007

### teffy3001

oh okay thanks a lot...so then to the last question though, the answer would be no? im just making sure....