Final answer:
Mapping a crime scene using rectangular coordinates involves measuring angles based on a reference frame, typically 90° to the coordinate system. A surveyor's example illustrates that for calculating distances, such as the width of a river, trigonometric functions like tangent can be used with the measured angle creating a right-angled triangle.
Step-by-step explanation:
When mapping a crime scene using rectangular coordinates, the angle that should be measured from the evidence to the surrounding walls and surfaces is determined by the reference frame being used, typically involving a 90° relations to the coordinate system. For example, in a case where a surveyor measures the width of a river, which flows directly north, starting directly across from a tree on the opposite bank, walking 100 m along the river to establish a baseline, the surveyor would then sight across to the tree. If the angle from the baseline to the tree is measured as 35°, the width of the river can be calculated using trigonometry, specifically the tangent function, because the surveyor has created a right-angled triangle.
In practical applications like accident investigation, the angle measured is often relative to a reference axis. For example, if the angle is described as 'east of north', it is measured counterclockwise from the positive x-direction (which represents east in this context). Consequently, the precise angle required to be measured depends on the specific circumstances and the established reference frame at the crime scene.