Why trigonometry is taught?

You will probably drive over a bridge or jump sometime in your life. That bridge was built using an understanding of forces acting at different angles because of the weight. You will notice that bridges involve many triangles, squares and other shapes trigonometry was used when designing the lengths and strengths of those triangles and squares so that they could determine the weight differential on the bridge. Also because the school's system thinks it's a required course for gradutaion.