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( a ) ${{1}^{{}^\circ }}$ (degree)

( b ) $1'$ (minute of arc or arcmin)

( c ) $1''$ ( second of arc or arc second) in radian.

Use ${{360}^{{}^\circ }}=2\pi rad$ , ${{1}^{{}^\circ }}=60'$ and $1'=60''$ .

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Before solving let's see what are degree measures and radian measures.

If a rotation from the initial side to terminal side is ${{\left( \dfrac{1}{360} \right)}^{th}}$ revolution, the angle is said to have a measure of on degree written as ${{1}^{{}^\circ }}$and ${{1}^{{}^\circ }}$ is divided into 60 minute and 1 minute is divided into 60 seconds, thus ${{1}^{{}^\circ }}=60'$ and $1'=60''$

Angles subtended at the centre by an arc of length of 1 unit in a unit circle that is a circle with radius 1 unit is said to have a measure of 1 radian.

Now, relation between degree and radian is $\text{2 }\!\!\pi\!\!\text{ radian=36}{{\text{0}}^{\text{ }\!\!{}^\circ\!\!\text{ }}}$, where $\pi =\dfrac{22}{7}$ or $\pi =3.14$

Now in question we have to find values of ${{1}^{{}^\circ }}$ (degree), $1'$ (minute of arc or arcmin), $1''$ ( second of arc or arc second) in radian.

Now, we know that $\text{2 }\!\!\pi\!\!\text{ radian=36}{{\text{0}}^{\text{ }\!\!{}^\circ\!\!\text{ }}}$

So, taking $\text{36}{{\text{0}}^{\text{ }\!\!{}^\circ\!\!\text{ }}}$ from numerator of right hand side to denominator of left hand side, we get

${{1}^{\text{ }\!\!{}^\circ\!\!\text{ }}}=\dfrac{2\pi }{360}$

On solving we get

${{1}^{\text{ }\!\!{}^\circ\!\!\text{ }}}=\dfrac{\pi }{180}$radian or approximately 0.07146 radian.

Now, we know that ${{1}^{{}^\circ }}=60'$

So, we can write${{1}^{\text{ }\!\!{}^\circ\!\!\text{ }}}=\dfrac{\pi }{180}$ as $60'=\dfrac{\pi }{180}$

Taking 60 from numerator of left hand side to denominator of right hand side, we get

$1'=\dfrac{\pi }{60\times 180}$radians

On solving we get

$1'=0.000291$ radians

Now, we also know that $1'=60''$

So, we can write$60'=\dfrac{\pi }{180}$ as $(60\times 60)''=\dfrac{\pi }{180}$

Taking $60\times 60$ from numerator of left hand side to denominator of right hand side, we get

$1''=\dfrac{\pi }{3600\times 180}$radians

On solving we get

$1''=0.00000485$ radians