What function you haven't even provided the formula
Yes (3, 28) is a solution for the equation.
In a right triangle the square on the hypotenuse is equal to the sums of the squares on the other two sides.
I'm guessing the equation should read something like

or possibly with minus signs in place of +.
Multiply both sides by
to get

Now substitute

to transform the equation to

which simplifies to

The ODE is now separable.

Integrate both sides. On the left, substitute




Solve for
.



Put this back in terms of
.

Put this back in terms of
.

Solve for
.




If you are considering all the vertices independently you will have a total of 8*10 = 80 triangles. You can figure out this way: the sum of the interior angles of a decagon = (2n-4)*right angles or (n-2)*triangles. So a decagon will form 8 triangles.
hope this helps...