A community for students.
Here's the question you clicked on:
 0 viewing
mathslover
 3 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)
mathslover
 3 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

mathslover
 3 years ago
Best ResponseYou've already chosen the best response.0I did the first one ... here : http://openstudy.com/study#/updates/511c70c9e4b06821731b25bc but second one is hard for me... can any1 help me?

.Sam.
 3 years ago
Best ResponseYou've already chosen the best response.0For 2nd one did you try to use the tirg identities? e.g. sin(A+B)=sinAcosB+cosAsinB

mathslover
 3 years ago
Best ResponseYou've already chosen the best response.0hmn... no but ok i will try it now..

mathslover
 3 years ago
Best ResponseYou've already chosen the best response.0But where and how to use that formula @.Sam.

mathslover
 3 years ago
Best ResponseYou've already chosen the best response.0OK leave it can any one prove that if : a + 2b + 3c = 0 then : \[\large{\frac{1}{2} + \frac{2}{b} + \frac{3}{c} = 0 }\]

.Sam.
 3 years ago
Best ResponseYou've already chosen the best response.0For \[3 \sin (\theta +\psi )+2 \sin (\theta +\Psi )+\sin (\psi +\phi )\] 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 )

mathslover
 3 years ago
Best ResponseYou've already chosen the best response.0But is that proving or just verifying ?

.Sam.
 3 years ago
Best ResponseYou've already chosen the best response.0its 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.
Ask your own question
Sign UpFind more explanations on OpenStudy
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
 Engagement 19 Mad Hatter
 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.