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sarihmanlapaz
 3 years ago
If cosA= 15/17 and A is in quadrant III, find cos 1/2A
sarihmanlapaz
 3 years ago
If cosA= 15/17 and A is in quadrant III, find cos 1/2A

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AravindG
 3 years ago
Best ResponseYou've already chosen the best response.1ya you have the value of cos A try to use the formula of cos 2A to get to the answer!!

AravindG
 3 years ago
Best ResponseYou've already chosen the best response.1@sarihmanlapaz did you try that?

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0what will i use in the 3 formula of cos2a?

AravindG
 3 years ago
Best ResponseYou've already chosen the best response.1just look at the equations and look at what we are trying to get the answer in terms of

AravindG
 3 years ago
Best ResponseYou've already chosen the best response.1we want cos A/2 isnt it?

AravindG
 3 years ago
Best ResponseYou've already chosen the best response.1and we have cos A , now you tell me which equation to use!!

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0i think cos^2  1

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0so how will i substitute it to that equation?

hartnn
 3 years ago
Best ResponseYou've already chosen the best response.0cosA=2cos^2(A/2)1 find cos(A/2) from here.

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0got it! thanks :)

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0but its none of the choices. >.< how can i solve it?

hartnn
 3 years ago
Best ResponseYou've already chosen the best response.0i m getting 0.2435, is that the option ?

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0oh no. haha my answer 0.2435 is in the options. i did'nt notice it.

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

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0its written in the question that the A is in quadrant 3

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

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0the options are. A).0.24054 B).0.24125 C) 0.24254 D) 0.24354

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0pls can you help me?

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

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0no. 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)

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0yes. yes :) i got the right answer 0.2425

hartnn
 3 years ago
Best ResponseYou've already chosen the best response.0how? the formula we gave and what u wrote are exactly the same...

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0http://www.themathpage.com/atrig/trigonometricidentities.htm

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0there is the formula for half angle :)

hartnn
 3 years ago
Best ResponseYou've already chosen the best response.0so 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)}

sarihmanlapaz
 3 years ago
Best ResponseYou've already chosen the best response.0yeah. thanks i got the right answer.
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