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!

Algebra: is this solvable?

  1. Apr 6, 2006 #1
    http://home.comcast.net/~andykovacs/equation.GIF [Broken]

    g is a constant. I need to find theta.

    Is there some trick I can do to cancel out the denominator in the root?
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Apr 6, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed


    and see what type of equation you get for y.
  4. Apr 6, 2006 #3


    User Avatar
    Science Advisor

    No, you can't cancel- but you can square. I would first divide the entire equation by [itex]g sin(\theta)[/itex] to get
    [tex]\frac{20}{g sin(\theta)}= \frac{14}{g sin(\theta)}+ \sqrt{\frac{14}{g sin(\theta)}}+ 8.41[/tex]
    I would even write it as
    [tex]\frac{10}{7}\frac{14}{g sin(\theta)}= \frac{14}{g sin(\theta)}+ \sqrt{\frac{14}{g sin(\theta)}}+ 8.41[/tex]
    because then I can let [itex]y= \frac{14}{g sin(\theta)}[/itex] and have
    [tex]\frac{10}{7}y= y+ \sqrt{y}+ 8.41[/tex]
    That gives
    [tex]\frac{3}{7}y- 8.41= \sqrt{y}[/tex]
    Square on both sides:
    [tex](\frac{9}{49}y- 8.41)^2= y[/itex]

    Solve that quadratic equation for y and then solve
    [tex] y= \frac{14}{g sin(\theta)}[/tex]
    for [itex]\theta[/itex].
    Last edited by a moderator: May 2, 2017
  5. Apr 6, 2006 #4
    Do you get y=-11.2432 and y=-1.0611 after solving the quadratic equation? If so then I probably screwed up with the physics.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Algebra solvable Date
Linear equation, point slope conversion Feb 26, 2018
How to solve this addition? Jan 7, 2018
Solvability of a certain equation Mar 18, 2013