Answer:
[tex]\cos(\frac25\pi) = \frac14(\sqrt5-1) \approx 0.3090[/tex]
[tex]\sin(\frac25\pi) = \sqrt{\frac58 + \frac{\sqrt5}{8}} \approx 0.9511[/tex]
[tex]\cos(2\pi) = 1[/tex]
The value of [tex]\frac{2\pi }{5}[/tex] radians corresponds to an angle of 180/5 = 72 degrees.
