Recent content by jlemus85

  1. J

    Show that a subset in E^2 is open.

    Hmmm... so I got sqrt(2) by applying pythagorean th. If my point is 1,0 and I drop the perpendicular from the line x equals y, then the sides of my triangle will be of length 1 and 1. Putting this into pyth eqn I get 1 plus 1 equals c squared. Solving I get c is equal to sqrt2. (sorry for the...
  2. J

    Show that a subset in E^2 is open.

    Dick, Thanks for your reply. I didn't realize I could be thinking about this on the x,y plane, duh. So the boundary line in other words is the line that goes through the origin aka the line y=x. So if I use x=1 and y=0 I get my r to be sqrt(2)? So then is it that r= sqrt(x1+x2)?
  3. J

    Show that a subset in E^2 is open.

    Thanks for your reply. I know what you're saying about using the given set, I just didn't want to put it in yet so as not to confuse people lol. But here goes. I know that d(p,q)= sqrt[ (x1-y1)^2 + (x2-y2)^2], given that p= (x1, y1) and q=(x2,y2). So if I draw a ball around Po (the...
  4. J

    Show that a subset in E^2 is open.

    Homework Statement Show that the subset of E^2 given by { (x1,x2) belonging to E^2 : x1>x2} is open. Homework Equations d(x,y)= sqrt[ (x1-y1)^2 +(x2-y2)^2 ] The Attempt at a Solution Ok so I would like someone to tell me if I'm on the right track or if I'm way off. So to...
  5. J

    Proving ~Au~B= ~(AnB): A Comprehensive Explanation with Examples

    Hi everyone, Was hoping I could get some help with the following: Note= ~ indicates the complement of Prove that: ~Au~B= ~(AnB) So far I have: Let x belong to ~Au~b then x belongs to ~A or x belongs to ~B. If x belongs to ~A then x is not in A thus x is not in ~AnB so x belongs to...
  6. J

    Area of a triangle in 3 space using cross product

    Hi all, I have a general question. When calculating the area of a triangle in 3 space, one applies the formula 1/2||axb||. Given three vertices, a,b,c...does it matter which vectors we choose to use (ab, bc, ac) as our a b vectors? Thanks!
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