Stop Everything

At some point Audrey needs to know the angle of a string coming from inside the volcano lab. Of course the actual angle cannot be measured because…it’s lava so she draws a normal with string and measures that then brings that to the higher cavity of the walls and measures that. All together with those angles, plus the lava angle forms a right triangle. Thus the two measured quantities can be subtracted from pi over 2 aka 90 degrees.