# How to find minima for non scalar-valued [closed]

I want to find minima. My code:

Formula = N[-{{{0.0, 0, 200.0} - 800.0 {0, 0, Cos[Tetha]}}.{Sin[Tetha] Cos[Phi],
Sin[Tetha] Sin[Phi], Cos[Tetha]}}]

DensPlot = DensityPlot[Formula, {Tetha, 0, 180}, {Phi, 0, 360},
ColorFunction -> "SunsetColors", PlotLegends -> Automatic,
FrameLabel -> {Style["θ0 (Degree)", FontSize -> 16],
Style["ϕ0 (Degree) ", FontSize -> 16]}, Mesh -> 10];

DensPlot


And now i'm trying to find minima. How we can see it is at 70 degree θ0.

Minimize[{Formula, 50 <= Tetha <= 100, 0 <= Phi <= 360}, {Tetha, Phi}]


I have next mistake:

Minimize::objfs: The objective function {0. -1. (200. -636620. Cos[Tetha])
Cos[Tetha]} should be scalar-valued. >>


If i tried to use FindMinimum:

FindMinimum[Formula, {{Tetha, #[]}, {Phi, #[]}}] & /@
{{0, 180}, {0, 360}}


I have next mistakes:

FindMinimum::nrnum: The function value {636420.} is not a real number at
{Tetha,Phi} = {0.,180.}. >>


and

FindMinimum::nrnum: The function value {636420.} is not a real number at
{Tetha,Phi} = {0.,360.}. >>


So my queation How I can find minima?

Formula = N[-({0.0, 0, 200.0} - 800.0 {0, 0, Cos[θ]}).{Sin[θ] Cos[ϕ], Sin[θ] Sin[ϕ], Cos[θ]}];