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sarihmanlapaz
Group Title
If cosA= 15/17 and A is in quadrant III, find cos 1/2A
 one year ago
 one year ago
sarihmanlapaz Group Title
If cosA= 15/17 and A is in quadrant III, find cos 1/2A
 one year ago
 one year ago

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AravindG Group TitleBest ResponseYou've already chosen the best response.1
ya you have the value of cos A try to use the formula of cos 2A to get to the answer!!
 one year ago

AravindG Group TitleBest ResponseYou've already chosen the best response.1
@sarihmanlapaz did you try that?
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
what will i use in the 3 formula of cos2a?
 one year ago

AravindG Group TitleBest ResponseYou've already chosen the best response.1
just look at the equations and look at what we are trying to get the answer in terms of
 one year ago

AravindG Group TitleBest ResponseYou've already chosen the best response.1
we want cos A/2 isnt it?
 one year ago

AravindG Group TitleBest ResponseYou've already chosen the best response.1
and we have cos A , now you tell me which equation to use!!
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
i think cos^2  1
 one year ago

AravindG Group TitleBest ResponseYou've already chosen the best response.1
\[2\cos^2 x1\]
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
so how will i substitute it to that equation?
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.0
cosA=2cos^2(A/2)1 find cos(A/2) from here.
 one year ago

AravindG Group TitleBest ResponseYou've already chosen the best response.1
@sarihmanlapaz gt it?
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
got it! thanks :)
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
but its none of the choices. >.< how can i solve it?
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.0
what did u get ?
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
0.2435
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.0
i m getting 0.2435, is that the option ?
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
oh no. haha my answer 0.2435 is in the options. i did'nt notice it.
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.0
but A/2 will be in 2nd quadrant where cos is negative. so we put minus 0.2435
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
its written in the question that the A is in quadrant 3
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.0
yes, A in 3rd,A/2 in 2nd. is 0.2435 in options?
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
the options are. A).0.24054 B).0.24125 C) 0.24254 D) 0.24354
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
pls can you help me?
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.0
since all options are positive, i guess A/2 goes in 1st quadrant...then 0.2435 is correct.
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
no. its wrong my friend. i just check the half angle formula. haha there is a formula for cosA/2 = squareroot of 1/2(1+A)
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.0
u mean ....(1+cos A) ?
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
yes. yes :) i got the right answer 0.2425
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.0
how? the formula we gave and what u wrote are exactly the same...
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
http://www.themathpage.com/atrig/trigonometricidentities.htm
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
there is the formula for half angle :)
 one year ago

hartnn Group TitleBest ResponseYou've already chosen the best response.0
so using that u got different answer? we gave u that formula only..... cosA=2cos^2(A/2)1 so cos(A/2)=sqrt{0.5*(1+cos A)}
 one year ago

sarihmanlapaz Group TitleBest ResponseYou've already chosen the best response.0
yeah. thanks i got the right answer.
 one year ago
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