the boat is 8 km north and 15 km west of its starting point.
Let its starting point = the origin of a graph.
This means that x = 0 and y = 0.
Let west be the horizontal line along the x-axis and let y = the vertical line along the y-axis.
15 km west of its starting point would be at x = 15.
8 km north of its starting point would be at y = 8
The point on the graph where the boat is located is (x,y) = (15,8).
the distance of the boat from its starting point is the hypotenuse of the right triangle formed by a horizontal line of 15 km in length and a vertical line of 8 km in length.
the length of this line is equal to the square root of 15^2 + 8^2 which makes it equal to the square root of 225 + 64 which makes it equal to the square root of 289 which makes it equal to 17 km.
a rough sketch of the graph is shown below:
x
(0,8) (15,8)
x x x
x x x
x x x
x x x
x x x
x x x
x x x
x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x
(0,0) (15,0)
x
x
x
x
x
x
coordinates are expressed as (x,y)
x is the value of the x-coordinate
y is the value of the y-coordinate