
Assuming acos is required, the following result was found.
the such but.. the following is free albeit as-the-crow flies. This makes use of an undocumented function in Zoho which is acos or inverse cosine. Just lifted from the JavaScript library figuring if it supports cos() then try this standard function....

bc1qf6elrdxc968h0k673l2djc9wrpazhqtxw8qqp4
0xb038962F3809b425D661EF5D22294Cf45E02FebF