- #1
Xhanger
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Homework Statement
12cot2(2x)=4
(8 exact answers)
3cos2(3x)=2sin(3x)
(6 decimal answers)
cos(3x)=sec(3x)+2tan2(3x)
(6 exact answers) hint(get all cosines) <- teacher wrote that
And then I have to prove by working on one side:
sin3(x) / 1-cosx = sinx*cosx+sinx
and
(sinx / cosx-1) + (sinx / cosx+1) = 2cosx / -sinx
Homework Equations
sin^2x + cos2x = 1 (and the other forms)
1+cot2x = csc2x
1+tan2x = sec2x
I can only use these forumulas, however you can rearrange the forumlas
The Attempt at a Solution
There were other problems of the prove by working on one side that I was able to figure out, so just a few beginning steps would do.
For:
12cot2(2x)=4
(8 exact answers)
This is my work, but its not right:
cot2(2x)=1/3
cot2(x)=1/3 (I changed 2x to x so that it would be easier, later I divide my answers by 2)
tan2x=3
tanx=+or-(squareroot(3))
tanx= (sin(sqroot(3)/2)) / cos(1/2) (this is where I divide by 2 because I made 2x -> x above)
So i get answers of +or- pi/3, 2pi/3, 5pi/3 which obviously isn't 8 answers...
Then for:
3cos2(3x)=2sin(3x)
(6 decimal answers)
I know how to start it by changing 3cos to 3 - 3sin using one of the pythag theories
but after that I am pretty much clueless
However on this one:
cos(3x)=sec(3x)+2tan2(3x)
(6 exact answers) hint(get all cosines) <- teacher wrote that (however someone told me that sec may be easier)
I am clueless on how to start it, which is the main problem. For most of these problems all I need is alittle help on how to start them.
Then on the ones that I need to prove by working on one side only:
sin3(x) / 1-cosx = sinx*cosx+sinx
and
(sinx / cosx-1) + (sinx / cosx+1) = 2cosx / -sinx
I only need a little help on how to start them or on how to go about solving them. As I said above I already solved a few of these on the paper, only I can't seem to grasp on how to start these specific ones.
Any help at all is appreciated and if anything is confusing please post and I will answers it ASAP.
Thanks in advance,
xhanger