# Eliminate parameter in parametric equation

1. ### teffy3001

23
so the question is:

eliminate the parameter in the pair of parametric equations

x = h + a secθ
y = k + b tanθ

to find the corresponding rectangular equation.

im taking an online course of calculus and i cant find an explanation of how to do this anywhere...ive been trying but it just doesnt make sense to me yet....any help?

2. ### Dick

25,852
sec^2(x)-tan^2(x)=1. So solve for the sec and tan, square and subtract.

3. ### teffy3001

23
how do i solve for sec and tan?
sorry but this calculus thing...its been a while for me

4. ### Dick

25,852
Not a calc question. x=h+a*sec(t), x-h=a*sec(t), (x-h)/a=sec(t). That sort of thing. Remember?

5. ### teffy3001

23
thanks, so if i do all that...then that answers my first question too?

6. ### Dick

25,852
You will have eliminated theta, right? Isn't that the problem?

7. ### teffy3001

23
i dont even know...this is so confusing. sorry to bother you with this....

8. ### Dick

25,852
Just try doing it. Solve for sec and tan - then square both expressions and subtract.

9. ### teffy3001

23
so i would get ((x-h)/a)^2 - ((y-k)/b)^2 = 1 ?

10. ### Dick

25,852
Exactly. That wasn't so bad, was it?

11. ### teffy3001

23
haha no thanks.