If tan frac{θ }{2} = t, then frac{{1 - {t^2}}}{{1 + {t^2}}} is equal to

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3.Trigonometrical Ratios, Functions and Identities

easy

If $\tan \frac{\theta }{2} = t,$then $\frac{{1 - {t^2}}}{{1 + {t^2}}}$is equal to

A

$\cos \theta $

B

$\sin \theta$

C

$\sec \theta $

D

$\cos 2\theta $

Solution

(a) $\tan \frac{\theta }{2} = t$

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

Standard 11

Mathematics

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