Question

Could use some help, got this question wrong twice-

Answer 1

(C) y= 3cos(4x),

Explanation:

When x=0, y=3. If we substitute x into the given equations, the possible answers are A,C or D.

Lets take C, y= 3cos(4x), and substitute x=π/2.

y= 3cos(4x) = 3cos(4*π/2)=3cos(2π)=3*1=3

This agrees with our graph. Choices B and D give wrong answers.