Question

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

• A. $\frac{1}{2}+\frac{\alpha \sqrt{3}}{120}$
• B. $\frac{1}{2}-\frac{\alpha }{120}$
• C. $\frac{1}{2}-\frac{\alpha \sqrt{3}}{120}$
• D. $\frac{1}{2}+\frac{\alpha }{120}$

Answer 1

Answer: (C)

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