Hello! In my book we have defined trigonometric functions for all angles. Everything is pretty much the same as when we were using acute angles (same ratio of sides), except that in a quadrant one trigonometric function might be positive, another might be negative, so on. The book has a table for the six functions (sine, cosine, and tangent and their reciprocals) and what their signs are in each quadrant. What makes the signs change? It's much easier for me to remember something if I understand it. Thanks.