Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Help with calculus

  1. Oct 11, 2010 #1
    1. The problem statement, all variables and given/known data

    1.Find the equation of the tangent plane at p=(0,0) on the surface z=f(x,y)=√(1-x²-y²)

    p is a vector.

    2.Give an intuitive geometric argument to support the result

    2. Relevant equations

    3. The attempt at a solution

    So I have no problem finding the equation of the tangent line. I am supposed to use the gradient to find it. But I don't really understand the second question. What is a geometric argument?

    Is it correct if I justify my answer by saying that the tangent plane is locally linear at p? Is that a geometric argument?

    Somehow, I feel that it is just not enough.

    Don't give me the answer please. Just a hind of what it means by "geometric argument."

    Thank You
  2. jcsd
  3. Oct 12, 2010 #2


    Staff: Mentor

    No. The surface z = f(x, y) = sqrt(1 - x^2 - y^2) represents a geometric figure. Your justification should involve this figure. If you knew what this figure was, you could work out the equation of the tangent plane in your head, without the use of calculus.
  4. Oct 14, 2010 #3
    Thank you very much. I'm still struggling with geometric interpretations but this surely helped.
  5. Oct 14, 2010 #4


    Staff: Mentor

    You're welcome.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook