Quantcast

A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

mathslover

  • 2 years ago

If sinθ+2sinϕ+3sinΨ=0 and cosθ+2cosϕ+3cosΨ=0 ; then evaluate : a) cos3θ+8cos3ϕ+27cos3Ψ b) sin(ϕ+ψ)+2sin(Ψ+θ)+3sin(θ+ψ)

  • This Question is Closed
  1. mathslover
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I did the first one ... here : http://openstudy.com/study#/updates/511c70c9e4b06821731b25bc but second one is hard for me... can any1 help me?

  2. .Sam.
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    For 2nd one did you try to use the tirg identities? e.g. sin(A+B)=sinAcosB+cosAsinB

  3. mathslover
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    hmn... no but ok i will try it now..

  4. mathslover
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    But where and how to use that formula @.Sam.

  5. mathslover
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    OK leave it can any one prove that if : a + 2b + 3c = 0 then : \[\large{\frac{1}{2} + \frac{2}{b} + \frac{3}{c} = 0 }\]

  6. .Sam.
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    For \[3 \sin (\theta +\psi )+2 \sin (\theta +\Psi )+\sin (\psi +\phi )\] You just use it for each term You'll get \[\small 3 \sin(\theta )\cos (\psi )+3\cos (\theta ) \sin (\psi )+2\sin (\theta ) \cos(\Psi )+2 \cos(\theta ) \sin(\Psi )+\cos(\psi ) \sin(\phi )+ \sin(\psi ) \cos (\phi )\] Then try to factor it and apply ( sinθ+2sinϕ+3sinΨ=0 and cosθ+2cosϕ+3cosΨ=0 )

  7. mathslover
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    But is that proving or just verifying ?

  8. .Sam.
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    its actually simplifying, try to factor that then your factored equation can apply this ( sinθ+2sinϕ+3sinΨ=0 and cosθ+2cosϕ+3cosΨ=0 ), which makes the equation smaller by equating them to 0.

  9. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.