I've got this drawing of a circle, and I'd like to know how I can calculate the distance between point A to point B in a straight line.
I already have:
Radius: 100
Arc length: 78.5
Angle: 45°
Post Script.: I don't really have a way to draw lines it's not a 2d object, it's just numbers on a console, thus I don't have visual feedback, I need to do it using those values above.
All you really need is the radius and the angle.
Draw a line between $A$ and $B$. Then mark the midpoint of this line as $C$.
Then, $\triangle OCB$ is a right-angled triangle with the right angle at $C$, meaning that $$\frac{\overline{CB}}{\text{radius}} = \sin\left(\frac\theta2\right)$$
and of course $\overline{AB}=2\ \overline{CB}$.