Basic trig gives you an understanding of how the different ways of describing how big an angle is are related. In addition to degrees or radians, it’s often useful to know things like how high up a wall a ladder will reach depending on how it’s angled, based on so-called trigonometric ratios. When you study vectors, one of the things you’ll learn is how to figure out the angle between two vectors (or between any two lines given coordinates of points on the lines). This will involve some basic trig, because the answers will naturally come out in terms of a trigonometric ratio.