1. Not finding help here? Sign up for a free 30min 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!

Sine in algebra

  1. Apr 10, 2008 #1
    in bsin30-85.7sin(theta)=0
    How can I make theta the subject?
     
  2. jcsd
  3. Apr 10, 2008 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Solve for sin(theta) and use arcsin.
     
  4. Apr 10, 2008 #3
    how is that done?
     
  5. Apr 10, 2008 #4
    It's the inverse.

    Recall ...

    [tex]y=x^2,x\geq0[/tex]

    [tex]f^{-1}(x)=\sqrt x[/tex]

    So similarly ...

    [tex]\sin x=y[/tex]

    [tex]\sin^{-1}y=x[/tex]
     
  6. Apr 10, 2008 #5
    so is this correct
    sin(theta)=-bsin30/-85.7
    1/sin(theta)=(-85.7)/(-binsin30)


    sin^-1(-bsin30/-85.7)=(theta)
     
    Last edited: Apr 10, 2008
  7. Apr 10, 2008 #6

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    That doesn't make it the subject, now does it? If sin(theta)=a, then theta=arcsin(a). That's the definition of arcsin.
     
  8. Apr 10, 2008 #7
    I forgot to add that arcsine is defined in Quadrants I & IV. It's domain is: [tex]-\frac{\pi}{2}\leq y\leq\frac{\pi}{2}[/tex].
     
  9. Apr 10, 2008 #8
    I think what you did was implied something like ... [tex]\frac{1}{x}=x^{-1}[/tex]

    It's not the same, the reciprocal of sine is cosecant. Refer to Dick's post.
     
  10. Apr 10, 2008 #9

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Yes. That's it. arcsin(b*sin(30)/85.7)=theta.
     
  11. Apr 11, 2008 #10
    That's it. arcsin(b*sin(30)/85.7)=theta.
    How do you work this out on a calculator?
     
  12. Apr 11, 2008 #11

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    To work it out on a calculator you need to know b, right? The arcsin function is usually labeled sin^(-1).
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Sine in algebra
  1. : sines (Replies: 6)

  2. Law of sines (Replies: 5)

  3. Law of sines (Replies: 2)

  4. Sine Regression (Replies: 2)

  5. Sine, cosine (Replies: 4)

Loading...