II.4.2

This has H = 2; II.3.13d can be used to solve it.

HAPPY
Let $$U\subset X$$ be the open set where the two morphisms agree; let $$ i \colon U \to Y$$ be the composition.
 * From the assumption construct a map $$ h \colon X \to Y \times Y$$; let $$h'$$ be its restriction to $$U$$
 * Argue (perhaps by a universal property) that $$h' = \Delta \circ i$$