When we are given a line cutting diagonally from one corner of a rectangle to the opposite corner, we are given two triangles.
300ft
____
| /|
| / |
| / |
| / |400ft
| / |
| / |
|/ |
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*not to scale
Now, using the right-angle trigonometry rule, we can find the hypotenuse (the diagonal line) which represents the footpath.
a^2 + b^2 = c^2
{where a is one side length, b is another side length, and c is the hypotenuse}
Thus, we make c the subject of the equation and substitute the other known values:
c^2 = 400^2 + 300^2
= 160,000 + 90,000
= 250,000
Now we move the 'squared' (^2) from the left hand side to the right hand side. When moving it across the equal sign (=) the result becomes the 'root' of itself:
c = _/250,000
= 500
Therefore, the length of the diagonal path is 500ft.
