1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Tangent/normal/area for this Circle

  1. Jun 3, 2004 #1
    I'm not whether this is the right place, but I saw geometry, n differentiation n thought, hmm, my question kinda involves both. If its in the wrong place, sorry...

    Anyways...Got this curve given as

    :biggrin: = theta for the sake of typing, hehe.

    x = a cos :biggrin: y = b sin :biggrin:

    I established it's a circle, because cos^2 :biggrin: +sin^2 :biggrin: =1

    and subbing that in what sin :biggrin: and cos :biggrin: equal gives (x/a)^2 + (y/b)^2 = 1

    Which is in the form for an equation for a circle? I'm not entirely sure on all this 2 be honest so if I'm goin wrong, feel free 2 point it out.

    I wanna find the tangent, the normal n the area of the circle. I've tried numerous ways but can't get the right answer.
  2. jcsd
  3. Jun 3, 2004 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    "I established it's a circle, because cos^2:grumpy: +sin^2:grumpy: =1"

    How does this identity establish the given curve as a circle?
    It is an ellipse!!
    The tangent is found by differentiating x and y with respect to :grumpy:
  4. Jun 3, 2004 #3
    You have made a mistake because the parametrised circle is given as:
    c(theta)=(a*cos(theta),a*sin(theta). (u have to take a=b)
    so to obtain its tangent we need to differentiate c w.r.t. theta, giving
    to obtain its normal we again differentiate t, giving
    hope that satisfies u..
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Tangent/normal/area for this Circle
  1. Tangent space (Replies: 17)