In the equation, cos θ = 20.8/33.6, θ =
cos θ = 20.8/33.6
Use the cosine inverse to find θ
arccos ( 20.8 / 33.6) = θ = about 51.75°
Since you are finding an angle you need to use inverse cos or arc cos.
On the web2 calc you do it like this
[2nd] [acos] (20.8/33.6) =
Make sure it is set to degrees or radians as needed... :)
