1. The problem statement, all variables and given/known data A box is held at rest on a smooth slope. The slope is inclined at an angle of 18◦ to the horizontal. Given that the normal reaction force between the box and the slope is 79 N, what is the mass of the box? 2. Relevant equations none 3. The attempt at a solution well, i posted a relatively easy example but i'm finding it hard to resolve it. i know about this triangle but im not too sure when i'm meant to use it and how it works. diagram annotated replies would be a real help. thanks!