Question 1205270
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Plot the points (-1,-4) and (3,-5) on the same xy grid.
Draw a segment to connect them. This forms the hypotenuse of a right triangle. 
{{{
drawing(400,400,-5,5,-8,2,
graph(400,400,-5,5,-8,2,-1000),
circle(-1,-4,0.06), circle(-1,-4,0.08), circle(-1,-4,0.1), circle(-1,-4,0.12),
circle(3,-5,0.06), circle(3,-5,0.08), circle(3,-5,0.1), circle(3,-5,0.12), 
circle(-1,-5,0.06), circle(-1,-5,0.08), circle(-1,-5,0.1), circle(-1,-5,0.12),
line(-1,-4,3,-5),
line(-1,-5,-1,-4),
line(-1,-5,3,-5),
locate(3+0.1,-5-0.1,"(3,-5)"),
locate(-1-1.2,-4+0.6,"(-1,-4)")
)
}}}

The horizontal leg of this right triangle is the distance between x coordinates.
The distance from x = -1 to x = 3 is 4 units.


The vertical leg of this right triangle is the distance between y coordinates.
The distance from x = -4 to x = -5 is 1 unit.


This right triangle has legs of a = 1 and b = 4
The hypotenuse c is the distance between (-1,-4) and (3,-5) 
Apply the Pythagorean Theorem to find c.
a^2 + b^2 = c^2
c = sqrt( a^2+b^2 )
c = sqrt( 1^2 + 4^2 )
c = sqrt(17)
c = 4.1231 units approximately


Because each unit represents 0.5 km, it means 4.1231 units = 4.1231*0.5 = 2.06155


Answer: The distance between the two landmarks is roughly 2.06 km
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