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: How do i solve this trig equation

  1. Apr 28, 2009 #1
    as part of a physics problem i get to one stage before the ansewr and then i get stuck here:

    0.15348=0.1415cosβ -0.291sinβcosβ

    how do i solve this equation with both sinβ and cosβ, i realise that i need to play with the identities but have had no luck,
    please help
    Last edited: Apr 28, 2009
  2. jcsd
  3. Apr 28, 2009 #2


    User Avatar
    Homework Helper

    Try squaring both sides and see if you can use sin2x+cos2x=1 in hopes to get one trig term.
  4. Apr 28, 2009 #3
    copied it all wrong, sorry, obviously cant work,,,

    meant to be

    0.15348=0.1415cosβ -0.291sinβcosβ

    if i square it i get

    0.023556=0.02cos2β +0.085sin2βcos2β-0.08sinβcosβ

    if i say cos2β=t

    0.023556=0.02t + 0.085(1-t)*(t)-0.08*[tex]\sqrt{1-t}[/tex][tex]\sqrt{t}[/tex]

    0.023556=0.02t + 0.085t - 0.085t2 -0.08[tex]\sqrt{t-t2}[/tex]

    0.023556=0.105t - 0.85t2 - 0.08[tex]\sqrt{t-t2}[/tex]

    now how would i find t??

    you sure theres no better way?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook