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Mathematics 15 Online
OpenStudy (zenmo):

Verify the Trigonometry Identity. Appreciate the help! :D

OpenStudy (zenmo):

\[2\tan(\cos^-1 (x+1)/2)=(\sqrt{16-4(x+1)^2})/(x+1)\]

OpenStudy (zenmo):

cos^-1=arccos

OpenStudy (anonymous):

okay so this requires a few trig identities.

OpenStudy (anonymous):

\[1+\tan^2(b)=\sec^2(b)=\frac{ 1 }{ \cos^2(b) }\]

OpenStudy (anonymous):

where \[b=\cos^{-1}(\frac{x+1}{2})\]

OpenStudy (anonymous):

Now we take the cos of both sides to obtain: \[\cos(b)=\frac{x+1}{2}\]

OpenStudy (anonymous):

Plug that into the trig identity above: \[1+\tan^2(b)=\frac{1}{\cos^2(b)}=\frac{1}{(\frac{x+1}{2})^2}\]

OpenStudy (anonymous):

Can you see where to go from here?

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