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3.Trigonometrical Ratios, Functions and Identities
easy
A circular wire of radius $7\,cm$ is cut and bend again into an arc of a circle of radius $12\,cm$. The angle subtended by the arc at the centre is ......$^o$
A
$50$
B
$210$
C
$100$
D
$60$
Solution
(b) Given that diameter of circular wire $= 14\,cm$
Therefore length of circular wire $= 14 \pi\, cm.$
$\therefore $ Required angle $ = \frac{{{\rm{arc}}}}{{{\rm{radius}}}} = \frac{{14\pi }}{{12}} = \frac{{7\pi }}{6}$
$ = \frac{7}{6}\pi .\frac{{{{180}^o}}}{\pi } = {210^o}$.
Standard 11
Mathematics
