Assuming the side lengths of the equilateral
triangular shaped doghouse are small enough
to allow the dog to encompass the doghouse in
it's travels... the area he can mark outside
of the doghouse is the area of the circle
as prescribed by a radius of 9.78m minus
the area of the triangular doghouse.
Area of circle: πr2 = 3.14(9.78)2 = 300.336 m2
For the triangle:
Area = (1/2)bh
Let x represent the length of a side of the doghouse in meters
The height can be found by use of Pythagorean theorem
Cutting the base in half to create two right triangles:
h2 + (0.5x)2 = x2
h2 + 0.25x2 = x2
h2 = 0.75x2
h = (√.75)x
h = 0.866x
Area = (1/2)(x)(.866x) = .866x2/2 = 0.433x2
The outside area the dog can mark is:
300.336 - 0.433x2 square meters
Andrew M.
04/11/17