Solving Cos trigonometric equation

Questions
,
1

Could you solve this equation please?

5*Cos[µ]=-1.7677669529663687

and please I need to find the solution in radian measuement and i also don’t know what is the procedure that solve it. I am looking forward to receive the answere.
many thanks

2 
eq = 5*Cos[x] == -1.7677669529663687;
sol = FindRoot[eq, {x, 0.1}];
5*Cos[x /. sol]

gives

-1.76776695296637

In[18]:= sol
Out[18]= {x -> 10.6342071636576}
3

Hi, my dear friend! Do you search the following solutions?

In[13]:= x = ArcCos[-1.7677669529663687/5];
K = x - Pi/2;
Table[(2 i - 1)/2*Pi + (-1)^(i - 1) K, {i, 5}]


Out[15]= {1.93216, 4.35102, 8.21535, 10.6342, 14.4985}

Peter

4

My dear friends Nasser and Peter,
I do feel grateful to have thise answers
Thank you very much indeed

5

Put this into Wolfram|Alpha ( LINK ):

Solve 5*Cos[x] == -1.7677669529663687