If $1^{\circ}=\alpha$ radians, then the approximate value of $\cos \left(60^{\circ} 1^{\prime}\right)$ is

If $1^{\circ}=\alpha$ radians, then the approximate value of $\cos \left(60^{\circ} 1^{\prime}\right)$ is
  1. $\frac{1}{2}+\frac{\alpha \sqrt{3}}{120}$
  2. $\frac{1}{2}-\frac{\alpha}{120}$
  3. $\frac{1}{2}-\frac{\alpha \sqrt{3}}{120}$
  4. $\frac{1}{2}+\frac{\alpha}{120}$

Solution

$\therefore \cos \left(60^{\circ} 1^{\prime}\right)=\frac{1}{2}-\frac{\alpha \sqrt{3}}{120}$

Asked in: AP EAMCET 2011

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