I have a project about 2-DoF inverted pendulum using joystick (X-Y degree value) sensor and holonomic robot. Because the inverted pendulum able to move in X-Y planes, I need to get $\theta$ from $\alpha$ degree and $\beta$. I've try the following equation from paper with the similar topic.
inverted pendulum visualization
$tan^2\theta = tan^2\alpha + tan^2\beta$
with $\alpha = 30^o$ and $\beta = 30^o$,
then I get result $\theta = 1.46085^o$
My question is, am I do it wrong because what I need is the degree value and the result seems to small for combination of two $30^o$ X-YDegree?
can somebody explain to me how to get the right angle value?