anonymous
  • anonymous
URGENT PLEASE: given that sin 2pi/7 = 0.7818 evaluate TO 4 decimal places: A) cos (3pi/14) B) cos (11pi/14)
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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jamiebookeater
  • jamiebookeater
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anonymous
  • anonymous
using equivalent algebraic expressions
TuringTest
  • TuringTest
pulling out trig cheat sheet...
anonymous
  • anonymous
ok lol...I will wait for you :D

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anonymous
  • anonymous
i just need the concept of how you go about doing these kinda questions...
TuringTest
  • TuringTest
actually I have to go do what I would do: look at this sheet for some relevant formulae http://tutorial.math.lamar.edu/pdf/Trig_Cheat_Sheet.pdf
TuringTest
  • TuringTest
make use of things like half-angle formulas, things like \(\sin(\frac\pi2-\theta)=\cos\theta\)
TuringTest
  • TuringTest
looks like you almost have \(\large \frac{2\pi}7=\frac{4\pi}{14}=\frac{\pi}{14}+\frac{3\pi}{14}\) so maybe some of those addition/subtraction formulas will come in handy
anonymous
  • anonymous
ok I get how I can manipulate the term in the middle of what is given for example in this care the 2pi/7 but how do I go from there to finding the cos 3pi/14 term
anonymous
  • anonymous
like I can say: \[\sin(\pi/14 +3\pi/14) = \sin(\pi/14)\cos(3\pi/14) +\cos(\pi/14)\sin(3\pi/14) \] but I don't know if that will help
TuringTest
  • TuringTest
you're basically trying the same type of stuff that I would, so continue looking at double-angle formulas to get that pi/14 argument to be a pi/7 argument I'm sorry I have to go, sorry to bail this time :( good luck!
anonymous
  • anonymous
lol its iight thanks a lot man, I like the cheat sheet btw
anonymous
  • anonymous
k wait i gotta read the question
anonymous
  • anonymous
haha i dont know what to do lol
anonymous
  • anonymous
its i got this one: so the solution is, for A) you say since \[\sin(\theta)=\cos({\pi/2} - \theta)\] then sin(4pi/14)= (cos pi/2 - 4pi/14) = cos (3pi/14) = 0.7818 for B) you use sin(theta) = -cos(pi/2+theta) and answer is= -0.7818
anonymous
  • anonymous
ohhh i see
anonymous
  • anonymous
haha i never done this stuff lol
anonymous
  • anonymous
it looks fun
anonymous
  • anonymous
yeh it is fun... I have done it 2 years ago, I cant remember anything now :S
anonymous
  • anonymous
haha i have never done this but like i wanna learn it but i am dead at this point. So i cant really think
anonymous
  • anonymous
i am actually gonna save that trig sheet on my comp. It is a good thing to have
anonymous
  • anonymous
yeh it is very good i love it :D
anonymous
  • anonymous
so who r u tutoring?
anonymous
  • anonymous
some guy I don't know
anonymous
  • anonymous
lol in ur neighbourhood?
anonymous
  • anonymous
how do you tutor? give me tips and stuff
anonymous
  • anonymous
kinda yeh
anonymous
  • anonymous
well i am tutoring a grade 8er so its diff
anonymous
  • anonymous
and do you ask them to tell you what they want you to teach them the day before?
anonymous
  • anonymous
umm i dont but if its hs math then yes u do
anonymous
  • anonymous
like u need to prepare
anonymous
  • anonymous
but like u explain the topic and then u do one example together and then u let the guy do another one on his own
anonymous
  • anonymous
and if he needs help then help him out on the way but try not to give away the answer
anonymous
  • anonymous
ok cool i get that, now lets say you get across a question that you don't know lol
anonymous
  • anonymous
what do you do in that case?
anonymous
  • anonymous
ummmm i just say i dont know but u shld say like i dont know this let me work this out and get back to u tom. ok like even if u dont tutor him th enext day like email him the answer
anonymous
  • anonymous
and if this guy is academically low then sometimes explaining the logic of a concept can confuse him so u just explain him the rules. It all depends on the student
anonymous
  • anonymous
i see.. yeh yeh i get what you mean
anonymous
  • anonymous
ok samjordan, amma go sleep am so tired
anonymous
  • anonymous
gd night.
anonymous
  • anonymous
ok bye

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