Angle in radian through which a pendulum swings if its length is 75, cm and tip describes an arc of

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3.Trigonometrical Ratios, Functions and Identities

easy

Find the angle in radian through which a pendulum swings if its length is $75\, cm$ and the tip describes an arc of length.

$21\,cm$

A

$\frac{7}{25}$

B

$\frac{7}{25}$

C

$\frac{7}{25}$

D

$\frac{7}{25}$

Solution

We know that in a circle of radius $r$ unit, if an arc of length $l$ unit subtends

An angle $\theta$ radian at the centre, then $\theta=\frac{l}{r}$

It is given that $r=75 \,cm$

Here, $l=21 \,cm$

$\theta=\frac{21}{75}$ radian

$=\frac{7}{25}$ radian

Standard 11

Mathematics

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