Answer:
[tex] { \boxed{ \tt{f(x) = 5 \cos3x \degree}}} \\ { \green{f(x) = f(60) : x = 60}}\\ f(60) = 5 \cos(3 \times 60) \degree \\ f(60) = 5 \cos(180 \degree) \\ but \: \cos(180 \degree) = - 1\\ { \boxed{ \bf{answer : f(60) = - 5}}} \\ \\ { \underline{ \blue{becker \: jnr}}}[/tex]
