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Mathematics 12 Online
OpenStudy (iwanttogotostanford):

Ver

OpenStudy (iwanttogotostanford):

@pooja195 i really need help

OpenStudy (legomyego180):

\[\frac{ \tan(x)+\pi }{ 2 }=-\cot(x)\]

OpenStudy (iwanttogotostanford):

please write out how to verify this one please

OpenStudy (legomyego180):

thinking about it.

Nnesha (nnesha):

i think the question is \[\tan(x) + \frac{\pi}{2} = -\cot(x)\] am i right ?

OpenStudy (legomyego180):

ah yea, that would make sense. then you could use cofunction identities I believe

Nnesha (nnesha):

or \[\tan(x+ \frac{\pi}{2})=-\cot(x)\]

OpenStudy (iwanttogotostanford):

yes thats correct @Nnesha

OpenStudy (legomyego180):

yup yup, trying to figure it out now

Nnesha (nnesha):

i hope you know that tanx = sinx/cosx \[\tan(x+\frac{\pi}{2})= \frac{\sin(x+\frac{\pi}{2})}{\cos(x+\frac{\pi}{2})}\]now you can apply sum/difference formula which is \[\large\rm \sin(x+y)= sin(x) cos(y)+\cos( x) \sin( y)\]\[\rm \cos(x+y)=\cos(x)\cos(y)-\sin(x)\sin(y)\]

OpenStudy (evoker):

That should work.

OpenStudy (iwanttogotostanford):

@Nnesha got it?

OpenStudy (iwanttogotostanford):

so @Nnesha proved it?

Nnesha (nnesha):

yes.apply sum formula ive posted above

OpenStudy (iwanttogotostanford):

thank you so much. @Nnesha

Nnesha (nnesha):

yw. let me know what you get. i can check your work

Nnesha (nnesha):

if you have any question..feel free to ask

OpenStudy (iwanttogotostanford):

I don't know how to apply it when I try... :-(

OpenStudy (iwanttogotostanford):

@Loser66

OpenStudy (loser66):

Can you post the original question by scanning?

OpenStudy (iwanttogotostanford):

Question: verify the identity: tan(x+π2)=−cot(x)

OpenStudy (loser66):

ok

OpenStudy (legomyego180):

\(\color{blue}{\text{Originally Posted by}}\) @Nnesha or \[\tan(x+ \frac{\pi}{2})=-\cot(x)\] \(\color{blue}{\text{End of Quote}}\)

OpenStudy (iwanttogotostanford):

oops I meant: tan(x+π/2)=−cot(x)

OpenStudy (loser66):

\(tan(x +\pi/2)=\dfrac{sin(x+\pi/2}{cos(x+\pi/2)}\) OK?

OpenStudy (iwanttogotostanford):

ok

OpenStudy (loser66):

Now, numerator: \(sin(x+pi/2)= sin xcos(\pi/2)+sin(\pi/2) cos x\) OK?

OpenStudy (iwanttogotostanford):

oh ok! got it so far.

OpenStudy (loser66):

but cos (pi/2) =0 and sin(pi/2)=1, so numerator = cos x OK?

OpenStudy (iwanttogotostanford):

ok

OpenStudy (loser66):

Now, denominator \(cos(x+\pi/2) = cos x cos(\pi/2) - sinxsin(\pi/2)\) again , \(cos(\pi/2) =0, sin(\pi/2) =1\) hence denominator = -sin x, ok?

OpenStudy (iwanttogotostanford):

ok

OpenStudy (loser66):

numerator/denominator = cos x/-sin x = -cot x that's it

OpenStudy (iwanttogotostanford):

ah ok. So that proved it all? I see now. Can you check one of my other proofs for me?

OpenStudy (loser66):

ok

OpenStudy (iwanttogotostanford):

thaks! Here it is:

OpenStudy (iwanttogotostanford):

1.) Verify the identity. quantity one minus sine of x divided by cosine of x equals cosine of x divided by quantity one plus sine of x -1 - sin x / cos x = cos x / 1 + sin x , then 1 - sin x / cos x X 1 + sin x / 1 + sin x then, 1 - sin^2 x/cos x (1 + sin x) , cos^2 x / cos x (1 + sin x), and then cos x / 1 + sin x.

OpenStudy (iwanttogotostanford):

So I listed the question and then the answer

OpenStudy (loser66):

math notation, please

OpenStudy (loser66):

one minus sine of x, but you wrote -1-sin(x) ???

OpenStudy (iwanttogotostanford):

the question was: Verify the identity: 1-sinx/cos x = cos x/ 1+sin x. I wrote: 1 - sin x / cos x = cos x / 1 + sin x , then 1 - sin x / cos x X 1 + sin x / 1 + sin x then, 1 - sin^2 x/cos x (1 + sin x) , cos^2 x / cos x (1 + sin x), and then cos x / 1 + sin x.

OpenStudy (loser66):

this is the trick!! You have to go from the left hand side to the right hand side, right? the denominator of the right hand side is (1+sinx) how to get it from the left hand side? just multiple both numerator and denominator of the left hand side by it!!

OpenStudy (loser66):

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