Question

f(x)= 3+5cos pi/3 (x-7)

If f(x)=4, solve for x.
Find 1st 3 positive values.

my answers: 2.31, 5.69, 8.31

Answer 1

3+5cos π/3(x-7) = 4

5 cos π/3(x-7) = 1
cos π/3(x-7) = .2
cosine is positive in I and IV

π/3(x-7) = 1.369438 or 2π-1.369438 = 4.913747

x-7 = 1.307717 or x-7 = 4.69228
x = 8.3077 or x = 11.69228

but you wanted the first 3 positive values
the period of your curve is
2π/(π/3) = 6
so by adding or subtracting 6 from any answer we obtain new answers

so 8.3077-6 = 2.3077
11.69228- 6 = 5.69228
and 8.31 is the third

hey, you had those, great job!!!!!