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We've seen yesterday conditions on  so that the canonical  process, , satisfyingThe condition is rather simple, since  should be a triangular region. But the proof is a bit more tricky...Recall that we want to parametrize the regionSince we have a true  process, then . Our polynomial is herewhere 's are the roots - in  - of . Consider now some kind of dual version of that polynomial,Having the roots of  outside the unit circle is the same as having the roots of  inside the unit circle. Obserse that we can writeRoots of  are thenFrom this point, we should discuss a little bit, depending on the value of .if Then there is one root, and only one. So we need to have  or equivalently .if Then we got roots in , andmeans, equivalently, thatif Then we have two (conjugate) roots in , and the square of norm of those roots is . Thus, .We get what was mention in the course: the canonical  has a stationary solution if, and only ifwhich is a triangular region, see