Quote:
Originally Posted by Gandalf
You only integrate over values where the density is positive. E.g., suppose you are considering the marginal density of y = .7. You don't want to include the point (.1, .7) since that is not within the shaded part of his diagram. The lowest value of x that has any density when y = .7 is x = .35.

Thank you, Gandalf. You are quite right. The graph in the solution has the area for which the density is positive marked with dotted lines, and this is the area over which we need to take integrals to calculate probabilities.
Yours,
Krzys'