Rewrite the given function as an equivalent function containing only cosine terms raised to a power of 1.f(x)=7cos^2x

Step-by-step explanation:

Using the double angle formulas,

cos(2x) = cos^2(x) - sin^2(x) (1)

1            = cos^2(x) + sin^2(x)(2)

add (1) and (2)

1 + cos(2x) = 2 cos^2(x)

=> cos^2(x) = (1/2) (1+cos(2x))  (3)

f(x) =  7 cos^2 (x)  

substituting (3)

f(x) = (7/2) (1+cos(2x))