In the triangular pyramid shown we consider four triangles (two right triangles on a common hinge unit length normal to a striped triangle with a dihedral $\delta$ angle and the outer big yellow triangle containing compound angle $\gamma$).
We derive Cosine Rule in Spherical trigonometry indirectly avoiding representation of sphere radius.
By applying Cosine Rule in striped triangle
$$ c^2= \tan^2\alpha+\tan^2\beta-2\tan\alpha \tan\beta \cos \delta $$
By applying Cosine Rule in larger yellow triangle containing compound angle $\gamma$
$$c^2= \sec^2\alpha+\sec^2\beta-2\sec\alpha \sec\beta \cos \gamma$$
Eliminate $c^2$ to simplify we get Cosine Rule in spherical trigonometry
$$\cos \gamma= \cos\alpha\cos\beta+ \sin \alpha \sin \beta \cos \delta $$
We have used plane trig and embedded a pyramid into $\mathbb R ^3 $ without explicit reference to a sphere:
Now how can we now draw the corresponding figure in hyperbolic geometry:
$$\cos \gamma= \cosh\alpha\cosh\beta+ \sinh \alpha \sinh \beta \cos \delta \,? $$
Considering simpler cases visualization... We can draw for right triangle $\delta= \pi/2$ the pyramid but how to at least draw it for hyperbolic geometry representation and result ?
$$ \cos \gamma= \cos\alpha\cos\beta \, \rightarrow \cos \gamma= \cosh\alpha\cosh\beta \,? $$
Thanks in advance for geometric considerations in hyperbolic geometry without explicitly bringing in the pseudosphere.
Regards