Answer:
[tex]g(x)=-5\cos (2x)[/tex]
Step-by-step explanation:
The given function is
[tex]f(x)=5\cos (2x)[/tex]
If a function reflected over the x-axis, then x-coordinate remains same but the sign of y-coordinate is changed.
[tex]P(x,y)\Rightarrow P'(x,-y)[/tex]
If function f(x) is a reflection over the x-axis to get the of g(x), then the resultant function is
[tex]g(x)=-f(x)[/tex]
Substituting the value of function f(x), we get
[tex]g(x)=-5\cos (2x)[/tex]
Therefore, the required function is [tex]g(x)=-5\cos (2x)[/tex].