MCQ
If $\tan \frac{\theta }{2} = t,$then $\frac{{1 - {t^2}}}{{1 + {t^2}}}$is equal to
  • $\cos \theta $
  • B
    $\sin \theta$
  • C
    $\sec \theta $
  • D
    $\cos 2\theta $

Answer

Correct option: A.
$\cos \theta $
a
(a) $\tan \frac{\theta }{2} = t$

$ \Rightarrow \frac{{1 - {{\tan }^2}\frac{\theta }{2}}}{{1 + {{\tan }^2}\frac{\theta }{2}}} = \cos \theta $.

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