Asked by Anonymous
Find the values of e,a,b,and c for r=21/5-2costheta?
Answers
Answered by
Steve
I assume you mean
r = 21/(5-2cosθ)
When you consider the general equation for a conic:
r = ep/(1 - e cosθ)
you see that you must set it up as
r = 21/[5(1 - 2/5 cosθ))
Now you can read off e and p. Since e<1, you have an ellipse. Now you need to use the distance to the directrix to determine a; then e will give you b and c.
r = 21/(5-2cosθ)
When you consider the general equation for a conic:
r = ep/(1 - e cosθ)
you see that you must set it up as
r = 21/[5(1 - 2/5 cosθ))
Now you can read off e and p. Since e<1, you have an ellipse. Now you need to use the distance to the directrix to determine a; then e will give you b and c.