Hello! To answer this exercise, we'll have to solve the alternatives and find which one equals 50ºF. Let's solve:
a.
[tex]\begin{gathered} y=15.\cos (2\pi)+35 \\ y=15.\cos (2.180)+35 \\ y=15.\cos (360)+35 \\ y=(15.1)+35 \\ y=50 \end{gathered}[/tex]
b.
[tex]\begin{gathered} y=-15.cos(2\pi)+35 \\ y=-15.cos(2.180)+35 \\ y=-15.cos(360)+35 \\ y=(-15.1)+35 \\ y=(-15)+35 \\ y=20 \end{gathered}[/tex]
c.
[tex]\begin{gathered} y=30.cos(2\pi)+15 \\ y=30.cos(2.180)+15 \\ y=30.cos(360)+15 \\ y=(30.1)+15 \\ y=30+15 \\ y=45 \end{gathered}[/tex]
d.
[tex]\begin{gathered} y=30.cos(2\pi)+35 \\ y=30.cos(2.180)+35 \\ y=30.cos(360)+35 \\ y=(30.1)+35 \\ y=30+35 \\ y=65 \end{gathered}[/tex]
So, the answer will be the first alternative: a. y = 15 cos2π +35
