Before the widespread introduction of electronic devices to measure distance, surveyors used a subtense bar to measure a distancex

that is not directly measurable. A subtense bar is a bar of known lengthhwith marks or "targets" at either end. The surveyor measures the angle formed by the location of the surveyor's scope and the top and bottom of the bar (this is the anglesubtendedby the bar). Since the angle and height of the bar are known, right triangle trigonometry can be used to find this horizontal distance. Alternatively, if the distance from the surveyor to the bar is large, then the distance can be approximated by the radiusr of the arcsintercepted by the bar.

A surveyor uses a subtense bar to find the distance across a river. If the angle of sight between the bottom and top marks on a2m

bar is4528", approximate the distance across the river between the surveyor and the bar. Round to the nearest meter.

Select one:

a.302m

b.76m

c.151m

d.605 m