trigonometry – How to cast this trigonometric polynomial into a convex function?

I’m trying to solve this minimization problem
begin{align}
min frac{1}{2}vec{w}^top vec{w}
end{align}

where
begin{align}
vec{w} =
begin{bmatrix}
f_1 begin{bmatrix}
mu sintheta\
mu costheta\
1
end{bmatrix} +
displaystylesum_{i=2}^n f_i begin{bmatrix}
mu vec{r}_i^top
[sintheta,
costheta,
-mu
]^top\
mu vec{v}_i^top
[stheta,
ctheta,
-mu
]^top\
1
end{bmatrix}
end{bmatrix},quad thetain[0,2pi]
end{align}

where $theta$ is the only variable and other vectors and scalars are given. Is it possible to recast this trigonometric polynomial into a convex function? Any help would be appreciated!