Mathematics
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OpenStudy (dls):
DE~!
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OpenStudy (dls):
\[y=\tan^{-1} \sqrt{\frac{1-cosx}{1+cosx}} \]
OpenStudy (dls):
I tried to solve till some extent
OpenStudy (anonymous):
well, you might notice that if the part behind there look very very similar to \(\tan \theta\) if you've done some rearranging.
OpenStudy (sirm3d):
and the answer is \[\large \frac{ dy }{ dx }=\frac{ 1 }{ 2 }\]right?
hartnn (hartnn):
try to get y=x/2.
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OpenStudy (dls):
\[\frac{dy}{dx}=\frac{1}{1+\frac{1-cosx}{1+cosx}} \times \frac{1}{2 \sqrt{\frac{1+cosx}{1-cosx}}} \times 1+\cos x d(\frac{1-cosx}{(1+cosx)^{2}}) - (1-cosx) d \frac{1+cosx}{(1+cosx) ^{2}} \]
OpenStudy (dls):
wth :o
OpenStudy (anonymous):
use the half angle formulas to reduce \(\sqrt \frac{1- \cos x}{1+\cos x}\) into \(\tan \frac{x}{2}\), then start differentiating.
hartnn (hartnn):
use
1-cos 2theta =... ?
1-sin 2theta=.....?
in terms of theta.
hartnn (hartnn):
*1+cos 2theta=...
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OpenStudy (dls):
2cos^2 theta
OpenStudy (dls):
where do i have to use it but?
hartnn (hartnn):
so, 1+cos x = 2cos^2 x
right ?
hartnn (hartnn):
*1+cos x = 2cos^2 (x/2)
OpenStudy (dls):
yeah! u confused me for a second :P
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hartnn (hartnn):
ans 1-cos x = ?
OpenStudy (dls):
-2cos(x/2)?
hartnn (hartnn):
no!
OpenStudy (dls):
:O
hartnn (hartnn):
1-cos 2theta = 2 sin^2 theta
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OpenStudy (dls):
yes
hartnn (hartnn):
so, 1-cos x = ?
OpenStudy (dls):
2sin sq theta/2
hartnn (hartnn):
2sin^2 x/2
now put this in your y=...
hartnn (hartnn):
what u get ?
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OpenStudy (dls):
2cos ^ theta/2sin ^ theta
OpenStudy (sirm3d):
2 theta on the LHS of the identity, theta on the RHS of the identity
x on the LHS, what do you think is the RHS?
OpenStudy (dls):
thatis powerr 2*
hartnn (hartnn):
yeah, and theres square root, so that simplifies to ?
OpenStudy (dls):
cos/sin
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OpenStudy (dls):
tan theta :o
hartnn (hartnn):
sin/cos = tan (x/2)
OpenStudy (dls):
yes
hartnn (hartnn):
so y=... ?
OpenStudy (dls):
tan inverse tan x/2
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OpenStudy (dls):
\[\frac{1}{1+\frac{\tan^{2}x}{4}} \]?
hartnn (hartnn):
\(\tan^{-1}(tan \theta) = \theta\)
OpenStudy (sirm3d):
tan^{-1} is supposed to "cancel" the tan, basic concept of an inverse function.
hartnn (hartnn):
\(\tan^{-1}(tan \: x/2) = x/2\)
OpenStudy (dls):
oh.! okay...thanks :D
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OpenStudy (dls):
Arigato senseis'!
hartnn (hartnn):
whats that ?
OpenStudy (dls):
Thank you,teacher(s) <3
OpenStudy (dls):
japanese phrase :P
hartnn (hartnn):
ohh! welcome ^_^
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OpenStudy (sirm3d):
sensei = teacher hahaha
OpenStudy (dls):
yeah ! :D