Tuesday, 2 July 2013

trigonometry - Solving sqrt3sin(phipi/6)=sin(phi)



The question is to solve:
3sin(ϕπ6)=sinϕ




I tried to turn it into asinϕbcosϕ=sinϕ,



Then I got 32sinϕ34cosϕ=sinϕ,



Therefore, 12sinϕ34cosϕ=0.



Then I turned it back into Rsin(ϕa)=0,



\implies (√13/4)\sin(ø-0.983)=0




So I think the solution should be \phi=n\pi+0.983



Is that correct? The answer on my book is n\pi+\frac \pi 3.(I made a mistake here, It should be π/3.)



Update: The reason why I got the wrong answer is because I forgot to √ that 4/3.



Thanks for pointing that mistake out :D.


Answer



It may be directly written that:

\sqrt3 \cos\phi= \sin \phi \implies \tan\phi = \sqrt{3} \implies \phi = n \pi + \dfrac{\pi}3 \text{ where }n\in \mathbb{Z}



Q.E.D.


No comments:

Post a Comment

real analysis - How to find lim_{hrightarrow 0}frac{sin(ha)}{h}

How to find \lim_{h\rightarrow 0}\frac{\sin(ha)}{h} without lhopital rule? I know when I use lhopital I easy get $$ \lim_{h\rightarrow 0}...