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Given: costheta= 4/5, sin x =12/13 ,theta is in the third quadrant, and x is in the fourth quadrant; evaluate cos 2x.
119/169
119/169
11/13
 one year ago
 one year ago
Given: costheta= 4/5, sin x =12/13 ,theta is in the third quadrant, and x is in the fourth quadrant; evaluate cos 2x. 119/169 119/169 11/13
 one year ago
 one year ago

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satellite73Best ResponseYou've already chosen the best response.1
you don't need the sine part
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
\[\cos(2x)=2\cos^2(x)1\]
 one year ago

tomhoffhimBest ResponseYou've already chosen the best response.0
dw:1364529999084:dw
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
oh i see there is a \(\theta\) and an \(x\)
 one year ago

aussy123Best ResponseYou've already chosen the best response.0
costheta= 4/5 I need cosx
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
you are asked for \(\cos(2x)\) where \(\sin(x)=\frac{12}{13}\)
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
\[\cos(2x)=12\sin^2(x)\]
 one year ago

aussy123Best ResponseYou've already chosen the best response.0
When I do it I get 169
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
there is no \(\theta \) in your question
 one year ago

tomhoffhimBest ResponseYou've already chosen the best response.0
ok, I'll do it for you, give me a second, this is an easy question
 one year ago

aussy123Best ResponseYou've already chosen the best response.0
yea I had to put theta for that
 one year ago

tomhoffhimBest ResponseYou've already chosen the best response.0
satellite, you don't know what you're doing..
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
\[\cos(x)=12\sin^2(x)\] \[\cos(x)=1(\frac{12}{13})^2\]\
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
\[\cos(2x)=1(\frac{12}{13})^2\] \[\cos(2x)=1\frac{144}{169}\]
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
\[\cos(2x)=\frac{25}{169}\]
 one year ago

aussy123Best ResponseYou've already chosen the best response.0
I know, thats what I get, but it isnt a choice
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
your question asks for \(\cos(2x)\) and doesn't mention any \(\theta\)
 one year ago

aussy123Best ResponseYou've already chosen the best response.0
I know but that is what is already given
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
oh damn i made a mistake!! sorry
 one year ago

tomhoffhimBest ResponseYou've already chosen the best response.0
I'm too lazy to do it but you need to draw the triangles and either use theta or x for the angle
 one year ago

aussy123Best ResponseYou've already chosen the best response.0
lol its okay, Ive made plenty
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
\[\cos(2x)=12\sin^2(x)\] \[\cos(2x)=12\times (\frac{12}{13})^2\] \[cos(2x)=12\times \frac{144}{169}\]
 one year ago

satellite73Best ResponseYou've already chosen the best response.1
\[\cos(2x)=1\frac{288}{169}\]\[\cos(2x)=\frac{119}{169}\]
 one year ago

aussy123Best ResponseYou've already chosen the best response.0
Lol this is a lot of work, can you use this same formula for tan2Theta
 one year ago

aussy123Best ResponseYou've already chosen the best response.0
nvm. I found the formula, Thank you!
 one year ago
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