1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Square roots and fractions

  1. Mar 17, 2008 #1
    How do you get 3/sqrt2 from 3sqrt2/2?
  2. jcsd
  3. Mar 17, 2008 #2
    Ask yourself what's (sqrt x)^2?
  4. Mar 17, 2008 #3

    Math Is Hard

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    hint: sqrt2/sqrt2 = 1
  5. Mar 17, 2008 #4
    sorry dont follow
  6. Mar 17, 2008 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Try going the other way.
    Start with
    [tex] \frac 3 {\sqrt 2} [/tex]

    to get

    [tex] \frac {3 \sqrt 2} 2 [/tex]
  7. Mar 17, 2008 #6
    If you're going from 3sqrt2/2 to 3/sqrt2 you're basically de-rationalizing the denominator.
  8. Mar 18, 2008 #7


    User Avatar
    Science Advisor

    By definition [itex](\sqrt{2})^2= \sqrt{2}\sqrt{2}= 2[/itex]. That means that
    [tex]\frac{\sqrt{2}}{2}= \frac{\sqrt{2}}{\sqrt{2}\sqrt{2}}[/tex]
  9. Mar 21, 2008 #8


    User Avatar

    [itex]\frac{3}{\sqrt 2} . \frac{\sqrt 2}{\sqrt 2} = \frac{3 \sqrt 2}{2}[/itex].

    This is rationalising the denominator as you cannot have a surd on the denominator. The question that you are asking is how you get the reverse, de-rationalising the denominator. Try opposite steps to the one I shown.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook