If Statement when x is near a value

Question

I am trying to solve the numerical equation:

sin^2(x)tan(x) = 0.499999

Using a while loop in C. However I was only able to get program to print an answer if

Answer 1

Well, a simple solution would be.

if (y >= x-x/100 && y <= x+x/100)
{
   [execute code...]
}

Essentially what it does is check if y is between [x minus 1% of x] and [x plus 1% of x]. Should work alright.