The graph above shows the two intersecting lines $x + y + 1 = 0$ and $2x - y - 1 = 0$, along with the angle between them, which is approximately $71.57^\circ$.

Let me know if you'd like any further details or clarifications.

Here are some related questions to expand on this topic:

1. How do you determine if two lines are parallel or perpendicular?
2. What is the meaning of the slope in the context of a graph?
3. How would the graph change if one of the slopes were modified?
4. How can you calculate the distance between a point and a line?
5. What is the geometric significance of the y-intercepts in this case?

Tip: When two lines are perpendicular, the product of their slopes is always $-1$.