Jean camps beside a wide river and wonders how wide it is She spots a large rock on the bank directly across from her She then walks upstream until she judges that the angle between her and the rock?

Jean can determine the width of the river by using basic trigonometry. By walking upstream until she forms a measurable angle with the rock directly across, she can create a right triangle where the distance she walked and the width of the river are the two legs. By measuring the angle and the distance she walked, she can apply the tangent function to calculate the width of the river. This method helps her find the river's width without needing to cross it directly.