Question

Write the function in term of the cofunction of a complementary angle

Answer 1

`\begin{gathered} \text{ Recall that cos x = sin (}(\pi)/(2)\text{ - x )} \\ \text{Therefore,} \\ \cos \text{ }(\pi)/(10)\text{ = sin (}(\pi)/(2)\text{ - }(\pi)/(10)) \\ \\ =\sin ((5\pi-\pi)/(10)) \\ =\text{ sin (}(4\pi)/(10)) \\ =\sin \text{ }(2\pi)/(5) \end{gathered}`