Question

2 cos a=1 i know this is easy for you guys but i dont understand the steps and where pi comes from! sorry!

Answer 1

You need a calculator to compute whatever the acosine of 1/2 is

Answer 2

not really, although you can use one. you start with
\[\cos(x)=\frac{1}{2}\] and then ask "what number has cosine one half?"

Answer 3

for that you can look on the unit circle and see where the first coordinate is 1/2
a good cheat sheet is attached below

Answer 4

Or you can memorize values of sine and cosine which is pretty easy

There's that too