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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

Mathematics
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you don't need the sine part
then how do I start
Two variables?

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Other answers:

\[\cos(2x)=2\cos^2(x)-1\]
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oh i see there is a \(\theta\) and an \(x\)
costheta= -4/5 I need cosx
you are asked for \(\cos(2x)\) where \(\sin(x)=-\frac{12}{13}\)
\[\cos(2x)=1-2\sin^2(x)\]
When I do it I get 169
a denominator of 169
there is no \(\theta \) in your question
ok, I'll do it for you, give me a second, this is an easy question
yea I had to put theta for that
satellite, you don't know what you're doing..
\[\cos(x)=1-2\sin^2(x)\] \[\cos(x)=1-(\frac{-12}{13})^2\]\
there is your 169
\[\cos(2x)=1-(\frac{12}{13})^2\] \[\cos(2x)=1-\frac{144}{169}\]
\[\cos(2x)=\frac{25}{169}\]
I know, thats what I get, but it isnt a choice
your question asks for \(\cos(2x)\) and doesn't mention any \(\theta\)
I know but that is what is already given
oh damn i made a mistake!! sorry
I'm too lazy to do it but you need to draw the triangles and either use theta or x for the angle
lol its okay, Ive made plenty
\[\cos(2x)=1-2\sin^2(x)\] \[\cos(2x)=1-2\times (\frac{12}{13})^2\] \[cos(2x)=1-2\times \frac{144}{169}\]
\[\cos(2x)=1-\frac{288}{169}\]\[\cos(2x)=-\frac{119}{169}\]
Lol this is a lot of work, can you use this same formula for tan2Theta
nvm. I found the formula, Thank you!

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